Methods and devices for ablation

ABSTRACT

An ablating device has a cover which holds an interface material such as a gel. The cover contains the interface material during initial placement of the device. The ablating device may also have a removable tip or a membrane filled with fluid. In still another aspect, the ablating device may be submerged in liquid during operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of applicationSer. No. 09/614,991, filed Jul. 12, 2000, which is acontinuation-in-part of application Ser. No. 09/507,336 filed Feb. 18,2000 which is a continuation-in-part of application Ser. No. 09/356,476,filed Jul. 19, 1999, which is a continuation-in-part of application Ser.No. 09/157,824, filed Sep. 21, 1998, which is a continuation-in-part ofapplication Ser. No. 08/943,683, filed Oct. 15, 1997, which is acontinuation-in-part of application Ser. No. 08/735,036, filed Oct. 22,1996, the full disclosures of which are incorporated herein byreference.

FIELD OF THE INVENTION

[0002] This invention relates generally to devices and methods forablating tissue. The diagnosis and treatment of electrophysiologicaldiseases of the heart, and more specifically to devices and methods forepicardial mapping and ablation for the treatment of atrialfibrillation, are described in connection with the devices and methodsof the present invention.

BACKGROUND OF THE INVENTION

[0003] Atrial fibrillation results from disorganized electrical activityin the heart muscle, or myocardium. The surgical maze procedure has beendeveloped for treating atrial fibrillation and involves the creation ofa series of surgical incisions through the atrial myocardium in apreselected pattern so as to create conductive corridors of viabletissue bounded by scar tissue.

[0004] As an alternative to the surgical incisions used in the mazeprocedure, transmural ablation of the heart wall has been proposed. Suchablation may be performed either from within the chambers of the heart(endocardial ablation) using endovascular devices (e.g. catheters)introduced through arteries or veins, or from outside the heart(epicardial ablation) using devices introduced into the chest. Variousablation technologies have been proposed, including cryogenic,radiofrequency (RF), laser and microwave. The ablation devices are usedto create elongated transmural lesions—that is, lesions extendingthrough a sufficient thickness of the myocardium to block electricalconduction—which form the boundaries of the conductive corridors in theatrial myocardium. Perhaps most advantageous about the use of transmuralablation rather than surgical incisions is the ability to perform theprocedure on the beating heart without the use of cardiopulmonarybypass.

[0005] In performing the maze procedure and its variants, whether usingablation or surgical incisions, it is generally considered mostefficacious to include a transmural incision or lesion that isolates thepulmonary veins from the surrounding myocardium. The pulmonary veinsconnect the lungs to the left atrium of the heart, and join the leftatrial wall on the posterior side of the heart. This location createssignificant difficulties for endocardial ablation devices for severalreasons. First, while many of the other lesions created in the mazeprocedure can be created from within the right atrium, the pulmonaryvenous lesions must be created in the left atrium, requiring either aseparate arterial access point or a transeptal puncture from the rightatrium. Second, the elongated and flexible endovascular ablation devicesare difficult to manipulate into the complex geometries required forforming the pulmonary venous lesions and to maintain in such positionsagainst the wall of the beating heart. This is very time-consuming andcan result in lesions which do not completely encircle the pulmonaryveins or which contain gaps and discontinuities. Third, visualization ofendocardial anatomy and endovascular devices is often inadequate andknowing the precise position of such devices in the heart can bedifficult, resulting in misplaced lesions. Fourth, ablation within theblood inside the heart can create thrombus which, in the right chambers,is generally filtered out by the lungs rather than entering thebloodstream. However, on the left side of the heart where the pulmonaryvenous lesions are formed, thrombus can be carried by the bloodstreaminto the coronary arteries or the vessels of the head and neck,potentially resulting in myocardial infarction, stroke or otherneurologic sequelae. Finally, the heat generated by endocardial deviceswhich flows outward through the myocardium cannot be preciselycontrolled and can damage extracardiac tissues such as the pericardium,the phrenic nerve and other structures.

[0006] What are needed, therefore, are devices and methods for forminglesions that isolate the pulmonary veins from the surrounding myocardiumwhich overcome these problems. The devices and methods will preferablybe utilized epicardially to avoid the need for access into the leftchambers of the heart and to minimize the risk of producing thrombus.

[0007] Additional aspects of the present invention are directed todevices and methods for ablating tissue. Ablation of heart tissue and,specifically, ablation of tissue for treatment of atrial fibrillation isdeveloped as a particular use of these other aspects of the presentinvention.

SUMMARY OF THE INVENTION

[0008] The present invention meets these and other objectives byproviding epicardial ablation devices and methods useful for creatingtransmural lesions for the treatment of atrial fibrillation.

[0009] In a first embodiment, a method of forming a transmural lesion ina wall of the heart adjacent to the pulmonary veins comprises the stepsof placing at least one ablation device through a thoracic incision andthrough a pericardial penetration so that at least one ablation deviceis disposed in contact with an epicardial surface of the heart wall;positioning at least one ablation device adjacent to the pulmonary veinson a posterior aspect of the heart while leaving the pericardialreflections intact; and ablating the heart wall with at least oneablating device to create at least one transmural lesion adjacent to thepulmonary veins. While the method may be performed with the heartstopped and circulation supported with cardiopulmonary bypass, themethod is preferably performed with the heart beating so as to minimizemorbidity, mortality, complexity and cost.

[0010] In another aspect of the invention, an apparatus for forming atransmural lesion in the heart wall adjacent to the pulmonary veinscomprises, in a preferred embodiment, an elongated flexible shaft havinga working end and a control end; an ablation device attached to theworking end for creating a transmural lesion in the heart wall; acontrol mechanism at the control end for manipulating the working end;and a locating device near the working end configured to engage one ormore of the pulmonary veins, or a nearby anatomical structure such as apericardial reflection, for positioning the working end adjacent to thepulmonary veins. The locating device may comprise a catch, branch, notchor other structure at the working end configured to engage one or moreof the pulmonary veins or other anatomical structure such as theinferior vena cava, superior vena cava, aorta, pulmonary artery, leftatrial appendage, right atrial appendage, or one of the pericardialreflections. The ablation device may be a radiofrequency electrode,microwave transmitter, cryogenic element, laser, ultrasonic transduceror any of the other known types of ablation devices suitable for formingtransmural lesions. Preferably, the apparatus includes a plurality ofsuch ablation devices arranged along the working end in a linear patternsuitable for forming a continuous, uninterrupted lesion around or on thepulmonary veins.

[0011] The working end may additionally include one or more movableelements that are manipulated from the control end and which may bemoved into a desired position after the working end has been locatednear the pulmonary veins. Slidable, rotatable, articulated, pivotable,bendable, pre-shaped or steerable elements may be used. Additionalablation devices may be mounted to these movable elements to facilitateformation of transmural lesions. The movable elements may be deployed topositions around the pulmonary veins to create a continuous transmurallesion which electrically isolates the pulmonary veins from thesurrounding myocardium.

[0012] In addition, a mechanism may be provided for urging all or partof the working end against the epicardium to ensure adequate contactwith the ablation devices. This mechanism may be, for example, one ormore suction holes in the working end through which suction may beapplied to draw the working end against the epicardium, or an inflatableballoon mounted to the outer side of the working end such that, uponinflation, the balloon engages the inner wall of the pericardium andforces the working end against the epicardium. This also functions toprotect extracardiac tissues such as the pericardium from injury byretracting such tissues away from the epicardial region which is beingablated, and, in the case of the balloon, providing an insulated barrierbetween the electrodes of the ablation probe and the extracardiactissues.

[0013] The apparatus may be either a single integrated device or two ormore devices which work in tandem. In either case, the apparatus mayhave two or more tips at the working end which are positioned onopposing sides of a tissue layer such as a pericardial reflection. Adevice may be provided for approximating the two free ends on opposingsides of the tissue layer, such as an electromagnet mounted to one orboth of the free ends. In this way, a continuous lesion may be createdin the myocardium from one side of the pericardial reflection to theother without puncturing or cutting away the pericardial reflection.

[0014] The apparatus may further include a working channel through whichsupplemental devices may be placed to facilitate visualization, tissuemanipulation, supplementary ablation, suction, irrigation and the like.

[0015] The apparatus and methods of the invention are further useful formapping conduction pathways in the heart (local electrograms) for thediagnosis of electrophysiological diseases. Any of the electrodes on theapparatus may be individually selected and the voltage may be monitoredto determine the location of conduction pathways. Alternatively, theapparatus of the invention may be used for pacing the heart bydelivering current through one or more selected electrodes at levelssufficient to stimulate heart contractions.

[0016] Additionally, although the ablation apparatus and methods of theinvention are preferably configured for epicardial use, the principlesof the invention are equally applicable to endocardial ablationcatheters and devices. For example, an endocardial ablation apparatusaccording to the invention would include a locating device configured toengage an anatomical structure accessible from within the chambers ofthe heart such as the coronary sinus (from the right atrium), pulmonaryartery (from the right ventricle), or the pulmonary veins (from the leftatrium), and the ablation device would be positionable in apredetermined location relative to the locating device. The endocardialapparatus could further include suction holes, expandable balloons, orother mechanisms for maintaining contact between the ablation device andthe interior surface of the heart wall.

[0017] In another aspect of the present invention, an anchor is used tohold part of the device while displacing another part of the device. Theanchor is preferably a balloon but may also be tines, a suction port ora mechanically actuated device. After actuating the anchor, a proximalportion of the device may be moved by simply manipulating the device orby advancement or withdrawal of a stylet.

[0018] The present invention is also related to a method of creating acontinuous ablation lesion in tissue underlying a pericardial reflectionwithout penetrating the pericardial reflection. First and secondablating devices are introduced into the space between the pericardiumand the epicardium. The first ablating device is positioned on one sideof the pericardial reflection and the second ablating device ispositioned on the other side of the pericardial reflection. Tissuebeneath the pericardial reflection is then ablated with one or both ofthe devices to create a continuous lesion beneath the pericardialreflection. The devices may be aligned across the pericardial reflectionby any suitable method such as with magnetic force, use of an emitterand sensor, or by marking the pericardial reflection on one side andlocating the mark from the other side of the pericardial reflection. Theemitter and sensor may work with electromagnetic radiation such aslight, ultrasound, magnetic field, and radiation.

[0019] In yet another aspect of the invention, the ablating device mayhave a guide portion which aligns the device between the pericardium andepicardium. The guide portion may be a continuous strap or a number ofdiscrete guide portions. The guide portions may be fins, wings or one ormore laterally extending elements such as balloons. The guide portionsmay be individually actuated to align the device and ablate discretelocations of the tissue along the ablating device.

[0020] The ablating device may also be advanced into position over aguide. The guide is preferably a guidewire but may be any other suitablestructure. The guide may also lock into position with a coaxial cable orlocking arm. The guide is advanced ahead of the ablation device andpositioned along the desired ablation path. The ablating device is thenadvanced or retracted along the guide. The ablating device preferablyincludes a device for locating previously formed lesions so thatsubsequent lesions will merge with a previously formed lesion to createa continuous, transmural lesion. The device for locating previouslycreated lesions may be pacing and sensing electrodes or electrodes whichsimply measure electrical impedance.

[0021] Although cutting through the pericardial reflections has certainrisks, the methods and devices of the present invention may, of course,be practiced while cutting through the pericardial reflections. Afterpenetrating through the pericardial reflection, the ablating device mayinterlock with another part of the same device or with a separatedevice.

[0022] In another method and device of the present invention, anotherablating device is provided which may be used to ablate any type oftissue including heart tissue for the reasons described herein. Theablating device has a suction well and an ablating element. The suctionwell adheres the device to the tissue to be ablated. The device ispreferably used to ablate cardiac tissue from an epicardial location toform a transmural lesion. The device preferably includes a number ofcells which each have a suction well and at least one ablating element.The cells are coupled together with flexible sections which permit thecells to displace and distort relative to one another. The devicepreferably has about 5-30 cells, more preferably about 10-25 cells andmost preferably about 16 cells. The suction well has an inner lip and anouter lip. The inner lip forms a closed wall around the ablatingelement.

[0023] The device also has a fluid inlet and a fluid outlet fordelivering and withdrawing fluid from within the closed wall formed bythe inner lip. The fluid is preferably a conductive fluid, such ashypertonic saline, which conducts energy from the ablating element, suchas an RF electrode, to the tissue. The fluid is preferably deliveredalong a short axis of the ablating element so that the temperaturechange across the ablating element is minimized.

[0024] The ablating elements are preferably controlled by a controlsystem. One or more temperature sensors on the device are coupled to thecontrol system for use as now described. The control system may controlablation in a number of different ways. For example, the control systemmay activate one or more pairs of adjacent cells to form continuouslesions between the adjacent cells. After ablation at the one or moreadjacent cells, another pair of adjacent cells is activated to formanother continuous ablation segment. This process is continued until acontinuous lesion of the desired geometry is produced. In another modeof operation, the control system may activate every other or every thirdcell. Still another mode of operation is to activate only the ablatingelements which have low temperatures by using a multiplexer coupled tothe temperature sensors.

[0025] The control system may also conduct a thermal response analysisof the tissue to be ablated to determine the appropriate ablationtechnique. The tissue to be ablated is heated, or cooled, and thetemperature response of the tissue over time is recorded. Thetemperature response is then analyzed to determine the appropriateablation technique. The analysis may be a comparison of the temperatureresponse against a database of temperature responses or may be acalculation which may require user input as described below.

[0026] In a further aspect of the invention, the ablating elementpreferably produces focused ultrasound in at least one dimension. Anadvantage of using focused ultrasound is that the energy can beconcentrated within the tissue. Another advantage of using focusedultrasound is that the energy diverges after reaching the focus therebyreducing the possibility of damaging tissue beyond the target tissue ascompared to collimated ultrasonic energy. When ablating epicardialtissue with collimated ultrasound, the collimated ultrasound energy notabsorbed by the target tissue travels through blood and remainsconcentrated on a relatively small area when it reaches another surfacesuch as the endocardial surface on the other side of a heart chamber.The present invention reduces the likelihood of damage to otherstructures since the ultrasonic energy diverges beyond the focus and isspread over a larger area. The focused ultrasound has a focal length ofabout 2 to 20 mm, more preferably about 2 to 12 mm and most preferablyabout 8 mm in at least one dimension. The focused ultrasound also formsan angle of 10 to 170 degrees, more preferably 30 to 90 degrees and mostpreferably about 60 degrees as defined relative to a focal axis. Thefocused ultrasound preferably emits over 90%, and more preferably over99%, of the energy within the angles and focal lengths described above.The focused ultrasound may be produced in any manner and is preferablyproduced by a curved transducer with a curved layer attached thereto.The ultrasound is preferably not focused, and may even diverge, whenviewed along an axis transverse to the focal axis.

[0027] The ultrasound transducers are preferably operated while varyingone or more characteristics of the ablating technique such as thefrequency, power, ablating time, and/or location of the focal axisrelative to the tissue. In a first treatment method, the transducer isactivated at a frequency of 2-7 MHz, preferably about 3.5 MHz, and apower of 80-140 watts, preferably about 110 watts, in short bursts. Forexample, the transducer may be activated for 0.01-1.0 second andpreferably about 0.4 second. The transducer is inactive for 2-90seconds, more preferably 5-80 seconds, and most preferably about 45seconds between activations. Treatment at this frequency in relativelyshort bursts produces localized heating at the focus. Energy is notabsorbed as quickly in tissue at this frequency as compared to higherfrequencies so that heating at the focus is less affected by absorptionin the tissue.

[0028] In a second treatment method, the transducer is operated forlonger periods of time, preferably about 1-4 seconds and more preferablyabout 2 seconds, to distribute more ultrasound energy between the focusand the near surface. The frequency during this treatment is also 2-14MHz, more preferably 3-7 MHz and preferably about 6 MHz. The transduceris operated for 0.7-4 seconds at a power of 20-60 watts, preferablyabout 40 watts. The transducer is inactive for at least 3 seconds, morepreferably at least 5 seconds and most preferably at least 10 secondsbetween each activation.

[0029] In a third treatment method, the ultrasonic transducer isactivated at a higher frequency to heat and ablate the near surface. Thetransducer is preferably operated at a frequency of at least 6 MHz andmore preferably at least 10 MHz and most preferably about 16 MHz. Thetransducer is operated at lower power than the first and secondtreatment methods since ultrasound is rapidly absorbed by the tissue atthese frequencies so that the near surface is heated quickly. In apreferred method, the transducer is operated at 2-10 watts and morepreferably about 5 watts. The transducer is preferably operated untilthe near surface NS temperature reaches 70-85 degrees C.

[0030] In general, the treatment methods described above deliver energycloser and closer to the near surface NS with each subsequent treatmentmethod. Such a treatment method may be practiced with other deviceswithout departing from this aspect of the invention and, as mentionedbelow, may be automatically controlled by the control system.

[0031] The device preferably has a number of cells with each cell havingat least one ablating element. After ablating tissue with all of thecells, gaps may exist between adjacent ablations. The tissue in the gapsis preferably ablated by moving at least one of the ablating elements.In one method, the entire device is shifted so that each cell is used asecond time to ablate one of the adjacent gaps. Yet another method ofablating tissue in the gaps is to tilt one or more of the ablatingelements to direct the ultrasound energy at the gaps between cells. Theablating element may be moved, tilted or pivoted in any suitable mannerand is preferably tilted with an inflatable membrane. The transducer mayalso simply be configured to direct ultrasound energy to tissue lyingbeneath the gaps between adjacent transducers. In this manner, thedevice does not need to be moved or tilted.

[0032] The device may be adhered to tissue with suction although suctionis not required. The device may also have a membrane filled with asubstance which transmits the ultrasound energy to the tissue. Themembrane conforms to the tissue and eliminates air gaps between thedevice and tissue to be ablated. Alternatively, the device may have asolid element which contacts the tissue and transmits the ultrasoundenergy to the tissue. The device may also be used with a gel applied tothe tissue which transmits the ultrasound energy and eliminates airgaps.

[0033] The device may also have a number of ultrasound transducers withvarying characteristics. For example, the device may have cells whichprovide focused ultrasound having different focal lengths or which areintended to operate at different frequencies or power. In this manner,the user may select the appropriate cell to ablate a particular tissuestructure. For example, it may be desirable to select an ablatingelement with a small focal length and/or low power when ablating thintissue.

[0034] An advantage of using ultrasound for ablating tissue is that thetransducer may be used for other measurements. For example, thetransducer may be used to provide temperature, tissue thickness,thickness of fat or muscle layers, and blood velocity data. Theultrasound transducer may also be used to assess the adequacy of contactbetween the device and the tissue to be ablated. These features findobvious use in the methods described herein and all uses of ultrasoundmentioned here, such as temperature feedback control, may beaccomplished using other methods and devices.

[0035] In another aspect of the invention, the ablating device has acover which extends over the bottom surface of the ablating device. Afluid cavity is defined by a space between the cover and bottom surface.A flowable material is positioned in the cavity. The device ispositioned in the desired ablation position and the cover is then movedto expose the bottom surface while leaving the flowable materialpositioned between the ablating device and the tissue to be ablated.

[0036] In still another aspect of the present invention, the device hasa flexible tip which facilitates advancement of the device. The tippreferably extends for at least two inches and is free of any ablatingelements. The tip is also preferably removable so that the tip also doesnot interfere with creating a closed loop.

[0037] In yet another aspect of the present invention, a fluidenvironment is created around the heart and the ablating device issubmerged in the fluid environment. The fluid environment helps toensure that no air bubbles or gaps are present and also can help toregulate the temperature by controlling the fluid temperature.

[0038] In still another aspect, a fluid-filled membrane is provided atthe contact or bottom surface of the device. The membrane preferablyconforms to the shape of the tissue to be ablated and may form a convexcontact surface. A fluid may also be circulated through the membrane toprovide cooling as necessary. The membrane may also have holes or may bepermeable to permit some of the fluid to leak from the membrane intocontact with the tissue being ablated.

[0039] Other aspects and advantages of the invention are disclosed inthe following detailed description and in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0040]FIG. 1A is side view of a left ablation probe according to theinvention.

[0041]FIG. 1B is a side view of a right ablation probe according to theinvention.

[0042] FIGS. 2A-2F are side views of a working end of the left ablationprobe of FIG. 1A in various configurations thereof.

[0043]FIG. 3 is a side cross-section of the working end of the leftablation probe of FIG. 1A.

[0044]FIG. 4 is a transverse cross-section of the shaft of the leftablation probe of FIG. 1A.

[0045] FIGS. 5A-C are partial side cross-sections of the working end ofthe left ablation probe of FIG. 1A, showing the deployment of a superiorsub-probe and inner probe thereof.

[0046]FIG. 6 is a side view of the left ablation probe of FIG. 1A.

[0047]FIG. 7 is a partial side cross-section of the handle of the leftablation probe of FIG. 1A.

[0048]FIG. 8 is an anterior view of the thorax of a patient illustratingthe positioning of the left and right ablation probes according to themethod of the invention.

[0049]FIG. 9 is a side view of the interior of a patient's thoraxillustrating the positioning of the left and right ablation probesaccording to the method of the invention.

[0050]FIG. 10 is a posterior view of a patient's heart illustrating theuse of the left and right ablation probes according to the method of theinvention.

[0051]FIG. 11 is a posterior view of a patient's heart illustrating atransmural lesion formed according to the method of the invention.

[0052]FIGS. 12 and 13 are side views of the left ablation probe of theinvention positioned on a patient's heart, showing a balloon and suctionports, respectively, on the inner probe.

[0053]FIG. 14A shows the ablating device having a pre-shaped distalportion.

[0054]FIG. 14B shows an alternative anchor.

[0055]FIG. 14C shows another anchor.

[0056]FIG. 14D shows still another anchor.

[0057]FIG. 15 shows the ablating device having a flexible distal portionwhich is shaped with a stylet.

[0058]FIG. 16 is a cross-sectional view of the ablating device of FIGS.14 and 15 with three chambers of the balloon inflated.

[0059]FIG. 17 is a cross-sectional view of the ablating device of FIGS.14 and 15 with two chambers of the balloon inflated.

[0060]FIG. 18 shows the ablating device advanced into the transversepericardial sinus with the balloon deflated.

[0061]FIG. 19 shows the ablating device advanced into the transversepericardial sinus with the balloon inflated.

[0062]FIG. 20 shows the ablating device extending between the left andright inferior pulmonary veins and another ablating device having an endsuperior to the right superior pulmonary vein.

[0063]FIG. 21 shows the ablating device moved toward the right superiorand right inferior pulmonary veins.

[0064]FIG. 22 shows one of the ablating devices having an emitter andthe other ablating device having a sensor for aligning the devicesacross a pericardial reflection.

[0065]FIG. 23 shows the ablating device having a needle to deliver amarker which is located on the other side of the pericardial reflection.

[0066]FIG. 24 shows the ablating device having a number of discreteguide portions.

[0067]FIG. 25 shows the guide portions being inflatable balloons.

[0068]FIG. 26 shows selective inflation of the balloons for selectiveablation along the ablating device.

[0069]FIG. 27A shows the guide portions used when ablating around thepulmonary veins.

[0070]FIG. 27B shows the guide portions being inflatable when ablatingaround the pulmonary veins.

[0071]FIG. 28 is a bottom view of another ablating device which isadvanced over a guide.

[0072]FIG. 29 is a top view of the ablating device of FIG. 28.

[0073]FIG. 30 is a cross-sectional view of the ablating device of FIGS.28 and 29 along line A-A of FIG. 29.

[0074]FIG. 31 is another cross-sectional view of the ablating device ofFIGS. 28 and 29 along line B-B of FIG. 29.

[0075]FIG. 32 shows the guide advanced to a desired location with theballoon deflated.

[0076]FIG. 33 shows the ablating device advanced over the guide andcreating a first lesion.

[0077]FIG. 34 shows the ablating device creating a second lesioncontinuous with the first lesion.

[0078]FIG. 35 shows the ablating device creating a third lesioncontinuous with the second lesion.

[0079]FIG. 36 shows another ablating device having an expandable devicemovable thereon.

[0080]FIG. 37 is a cross-sectional view of the ablating device of FIG.36.

[0081]FIG. 38 is an enlarged view of the cross-sectional view of FIG.37.

[0082]FIG. 39 shows the ablating device with a piercing element in aretracted position.

[0083]FIG. 40 shows the ablating device aligned across the pericardialreflection.

[0084]FIG. 41 shows the ablating device interlocked with anotherablating device on opposite sides of the pericardial reflection.

[0085]FIG. 42 shows a mechanism for locking the first and secondablating devices together.

[0086]FIG. 43 shows the piercing element engaging a lock on the otherablating device.

[0087]FIG. 44 shows the ablating device passing through the pericardialreflection and interlocking with itself.

[0088]FIG. 45 shows the ablating devices interlocked across thepericardial reflections.

[0089]FIG. 46 shows the ablating device adhered to a pericardialreflection with suction.

[0090]FIG. 47 shows the penetrating element penetrating the pericardialreflection.

[0091]FIG. 48 shows the ablating device passing through the pericardialreflection.

[0092]FIG. 49 shows another ablating device.

[0093]FIG. 50 shows a buckle for forming a closed loop with the ablatingdevice.

[0094]FIG. 51 shows another buckle for forming the closed loop with theablating device.

[0095]FIG. 52 shows a bottom side of the ablating device of FIG. 49.

[0096]FIG. 53A is a cross-sectional view of the ablating device alongline C-C of FIG. 52.

[0097]FIG. 53B is an alternative cross-sectional view of the ablatingdevice along line C-C of FIG. 52.

[0098]FIG. 54 is a cross-sectional view of the ablation device alongline D-D of FIG. 53A showing a fluid inlet manifold.

[0099]FIG. 55 is a cross-sectional view of an alternative embodiment ofthe device.

[0100]FIG. 56 shows a system for controlling the ablation device of FIG.55.

[0101]FIG. 57 shows the device having two sets of lumens extending fromeach end of the device toward the middle of the device.

[0102]FIG. 58 shows another ablating device.

[0103]FIG. 59 is an exploded view of a cell of the ablating device.

[0104]FIG. 60 is a cross-sectional view of the ablating device of FIG.60.

[0105]FIG. 61 is a perspective view of a transducer with a layerattached thereto.

[0106]FIG. 62 is an end view of the transducer and layer.

[0107]FIG. 63 is a plan view of the transducer and layer.

[0108]FIG. 64 shows another ablating device with a membrane filled witha substance with transmits energy from the transducer to the tissue.

[0109]FIG. 65 shows the membrane inflated to move the focus relative tothe tissue.

[0110]FIG. 66 shows another ablating device with a membrane which tiltsthe device when inflated.

[0111]FIG. 67 shows another ablating device.

[0112]FIG. 68 shows still another ablating device having at least twoablating elements which have different ablating characteristics.

[0113]FIG. 69 is an isometric view of another ablating element whichdiverges in at least one dimension to ablate tissue beneath gaps betweenablating elements.

[0114]FIG. 70 is a side view of the ablating element of FIG. 69.

[0115]FIG. 71 shows still another device for ablating tissue.

[0116]FIG. 72 is a partial cross-sectional view showing three ablatingelements which are movable within a body of the device.

[0117]FIG. 73 shows the ablating elements with the body removed.

[0118]FIG. 74 shows the ablating device having a cover.

[0119]FIG. 75 shows a system for ablating tissue which provides a liquidenvironment around the heart.

[0120]FIG. 76 shows another system for providing a liquid environmentaround the heart.

[0121]FIG. 77 shows another system for ablating tissue with a membraneextending over the ablating element.

[0122]FIG. 78 shows the membrane extending over a number of ablatingelements.

[0123]FIG. 79 shows a flexible skirt surrounding the ablating element.

[0124]FIG. 80 shows another embodiment of the flexible skirt.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0125] FIGS. 1A-1B illustrate a first embodiment of the apparatus of theinvention. In this embodiment, the apparatus comprises a left ablationprobe 20, shown in FIG. 1A, and a right ablation probe 22, shown in FIG.1B, which work in tandem to form a transmural lesion isolating thepulmonary veins from the surrounding myocardium. Left ablation probe 20has a flexible shaft 21 extending to a working end 24 configured forinsertion into the chest cavity through a small incision, puncture oraccess port. Opposite working end 24, shaft 21 is attached to a controlend 26 used for manipulating the working end 24 from outside the chest.Shaft 21 is dimensioned to allow introduction through a small incisionin the chest, preferably in a subxiphoid location, and advanced to thepulmonary veins on the posterior side of the heart. Preferably, shaft 21is configured to be flexible about a first transverse axis to allowanterior-posterior bending and torsional flexibility, but relativelystiff about a second transverse axis perpendicular to the firsttransverse axis to provide lateral bending stiffness. In an exemplaryembodiment, shaft 21 has a length in the range of about 10-30 cm, and aguide portion 25 having a rectangular cross-section with awidth-to-height ratio of about 2-5, the cross-sectional width beingabout 6-35 mm and the cross-sectional height being about 3-17 mm. Theguide portion 25 aligns the device between the epicardium andpericardium to ablate tissues as described below. Shaft 21 is made of aflexible biocompatible polymer such as polyurethane or silicone, andpreferably includes radiopaque markers or a radiopaque filler such asbismuth or barium sulfate.

[0126] Working end 24 includes a plurality of ablating elements 27. Theablating elements 27 are preferably a plurality of electrodes 28 fordelivering radiofrequency (RF) current to the myocardium so as to createtransmural lesions of sufficient depth to block electrical conduction.Electrodes 28 may be partially-insulated solid metal rings or cylinders,foil strips, wire coils or other suitable construction for producingelongated lesions. Electrodes 28 are spaced apart a distance selected sothat the lesions created by adjacent electrodes contact or overlap oneanother, thereby creating a continuous, uninterrupted lesion in thetissue underlying the electrodes. In an exemplary embodiment, electrodes28 are about 2-20 mm in length and are spaced apart a range of 1-6 mm.It is understood that the term electrodes 28 as used herein may refer toany suitable ablating element 27. For example, as an alternative to RFelectrodes, the ablating elements 27 may be microwave transmitters,cryogenic element, laser, heated element, ultrasound, hot fluid or othertypes of ablation devices suitable for forming transmural lesions. Theheated element may be a self-regulating heater to prevent overheating.Electrodes 28 are positioned so as to facilitate lesion formation on thethree-dimensional topography of the left atrium. For example, lateralelectrodes 28 a face medially to permit ablation of the myocardium onthe lateral side of the left inferior pulmonary vein and medialelectrodes 28 b face anteriorly to permit ablation of the posteriorsurface of the myocardium adjacent to the left inferior pulmonary vein.

[0127] Working end 24 further includes a locating mechanism whichlocates the working end at one of the pulmonary veins and helps tomaintain it in position once located. In a preferred embodiment, workingend 24 is bifurcated into two branches 30, 32, and the locatingmechanism is a notch 34 disposed between the two branches. Notch 34tapers into a concave surface 36 so as to receive one of the pulmonaryveins between branches 30, 32 and to atraumatically engage the pulmonaryvein against concave surface 36. In an exemplary embodiment, notch 34 isabout 10 to 30 mm in width at its widest point between branches 30, 32and tapers toward concave surface 36 which has a radius of curvature ofabout 4 to 15 mm, so as to conform to the outer curvature of thepulmonary vein. Preferably, notch 34 is sized and positioned forplacement against the left inferior pulmonary vein, as described morefully below. Alternatively, the locating mechanism may be configured toengage another anatomic structure such as the inferior vena cava,superior vena cava, pericardial reflections, pulmonary vein, aorta,pulmonary artery, atrial appendage, or other structure in the spacebetween the pericardium and the myocardium. The various shapes of theablating devices described and shown herein are, of course, useful inlocating various structures to position the ablating elements againstpredetermined tissues to be ablated.

[0128] Working end 24 further includes a superior sub-probe 38 and aninferior sub-probe 40 which are slidably extendable from working end 24,as further described below.

[0129] Control end 26 includes a handle 42 and a plurality of slidableactuators 44A-44E, which are used to extend superior sub-probe 38 andinferior sub-probe 40 from working end 24, and to perform otherfunctions as described below. An electrical connector 46 suitable forconnection to an RF generator is mounted to handle 42 and iselectrically coupled to electrodes 28 at working end 24. Also mounted tohandle 42 are a working port 48 in communication with a working channel92, described below, and a connector 50 for connection to a source ofinflation fluid or suction, used for purposes described below.

[0130] Right ablation probe 22 has a flexible shaft 52 extending from acontrol end 54 to a working end 56. Working end 56 has a cross-member 58to which are mounted a plurality of electrodes 60. Cross member 58preferably has tips 59 which are pre-shaped or deflectable into a curveso as to conform to the right lateral walls of the right pulmonaryveins, and which are separated by a distance selected so that the tworight pulmonary veins may be positioned between them, usually a distanceof about 20-50 mm. Electrodes 60 are sized and positioned so as tocreate a continuous lesion along the right side (from the patient'sperspective) of the pulmonary veins as described more fully below. In anexemplary embodiment, electrodes 60 are about 2-20 mm in length, and arespaced apart about 1-6 mm. Shaft 52 is dimensioned to allow introductionthrough a small incision in the chest, preferably in a subxiphoidlocation, and advanced to the pulmonary veins on the posterior side ofthe heart. Shaft 52 will have dimensions, geometry and materials likethose of shaft 21 of left ablation probe 20, described above.

[0131] Control end 54 includes a handle 62. An electrical connector 64adapted for connection to an RF generator is attached to handle 62 andis electrically coupled to electrodes 60 at working end 56. An inflationor suction connector 65 is mounted to handle 62 and adapted forconnection to a source of inflation fluid or suction, for purposesdescribed below. Handle 62 may further include a working port (notshown) like working port 48 described above in connection with leftablation probe 20.

[0132] FIGS. 2A-2E illustrate the deployment of the various componentsof working end 24 of left ablation probe 20. Superior sub-probe 38 isslidably extendable from working end 24 as shown in FIG. 2B. A pluralityof electrodes 66 are mounted to superior sub-probe 38 and are sized andpositioned to create a continuous lesion along the left side of thepulmonary veins. Superior sub-probe 38 has an articulated or steerablesection 68 which can be selectively shaped into the position shown inFIG. 2C, with its distal tip 70 pointing in a lateral direction relativeto the more straight proximal portion 72.

[0133] As shown in FIG. 2D, an inner probe 74 is slidably extendablefrom superior sub-probe 38 and is directed by steerable section 68 in alateral direction opposite notch 34. Inner probe 74 is separated fromnotch 34 by a distance selected such that inner probe 74 may bepositioned along the superior side of the pulmonary veins when the leftinferior pulmonary vein is positioned in notch 34. In an exemplaryembodiment, the maximum distance from concave surface 36 to inner probe74 is about 20-50 mm. A plurality of electrodes 76 are mounted to innerprobe 74 and positioned to enable the creation of a continuoustransmural lesion along the superior side of the pulmonary veins asdescribed more fully below.

[0134] Referring to FIG. 2E, inferior sub-probe 40 is slidablyextendable from working end 24. Its distal tip 78 is attached to atether 80 extending through a lumen in shaft 21. Tether 80 may beselectively tensioned to draw distal tip 78 away from inner probe 74(toward control end 26), imparting a curvature to inferior sub-probe 40.Inferior sub-probe 40 is constructed of a resilient, bendable plasticwhich is biased into a straight configuration. When inferior sub-probe40 has been advanced sufficiently, tether 80 may be released, wherebythe resiliency of inferior sub-probe 40 causes it to conform to thepericardial reflection and the medial and/or inferior sides of the fourpulmonary veins. Inferior sub-probe 40 further includes a plurality ofelectrodes 82 sized and positioned to produce a continuous transmurallesion in the myocardium along the inferior side of the pulmonary veins,as described more fully below.

[0135] Referring to FIGS. 3 and 4, superior sub-probe 38 is slidablydisposed in a first lumen 84 and inferior sub-probe 40 is slidablydisposed in a second lumen 86 in shaft 21. Electrodes 28 along notch 34are coupled to wires 88 disposed in a wire channel 90 running beneathelectrodes 28 and extending through shaft 21. Each electrode is coupledto a separate wire to allow any electrode or combination of electrodesto be selectively activated. Shaft 21 also includes a working channel 92extending to an opening 94 in working end 24 through which instrumentssuch as endoscopes, suction/irrigation devices, mapping and ablationdevices, tissue retraction devices, temperature probes and the like maybe inserted. Superior sub-probe 38 has an inner lumen 96 in which innerprobe 74 is slidably disposed. Electrodes 76 on inner probe 74 arecoupled to wires 98 extending through inner probe 74 to connector 46 onhandle 42, shown in FIG. 1A. Similarly, electrodes 66 on superiorsub-probe 38 are coupled to wires 99 (FIG. 4) and electrodes 82 oninferior sub-probe 40 are coupled to wires 100, both sets of wiresextending to connector 46 on handle 42. Tether 80 slidably extendsthrough tether lumen 102 in shaft 21.

[0136] The distal end of inner probe 74 has a tip electrode 104 forextending the transmural lesion produced by electrodes 76. Preferably,inner probe 74 further includes a device for approximating the tip ofinner probe 74 with the superior tip 106 of right ablation probe 22(FIG. 1B) when the two are separated by a pericardial reflection. In apreferred embodiment, a first electromagnet 108 is mounted to the distalend of inner probe 74 adjacent to tip electrode 104. First electromagnet108 is coupled to a wire 110 extending to handle 42, where it is coupledto a power source and a switch (not shown) via connector 46 or aseparate connector. Similarly, a second electromagnet 112 is mounted todistal tip 78 of inferior sub-probe 40, adjacent to a tip electrode 114,which are coupled to wires 116, 118 extending to a connector on handle42. As shown in FIG. 1B, a third electromagnet 120 is mounted tosuperior tip 106 of right ablation probe 22, and a fourth electromagnet122 is mounted to inferior tip 124 of right ablation probe 22.Electromagnets 120, 122 are coupled to wires (not shown) extending to aconnector on handle 62 for coupling to a power source and switch. Inthis way, superior tip 106 and inferior tip 124 may be approximated withinner probe 74 and inferior sub-probe 40 across a pericardial reflectionby activating electromagnets 108, 112, 120, 122.

[0137] It should be noted that thermocouples, thermistors or othertemperature monitoring devices may be mounted to the working ends ofeither left or right ablation probes 20, 22 to facilitate temperaturemeasurement of the epicardium during ablation. The thermocouples may bemounted adjacent to any of the electrodes described above, or may bewelded or bonded to the electrodes themselves. The thermocouples will becoupled to wires which extend through shafts 21, 52 alongside theelectrode wires to connectors 46, 64 or to separate connectors onhandles 42, 62, facilitating connection to a temperature monitoringdevice.

[0138] FIGS. 5A-5C illustrate the operation of superior sub-probe 38.Superior sub-probe 38 has a pull wire 126 movably disposed in a wirechannel 128 in a sidewall adjacent to inner lumen 96. Pull wire 126 isfixed at its distal end 130 to steerable section 68 of superiorsub-probe 38. Steerable section 68 is constructed of a flexible,resilient plastic such that by tensioning pull wire 126, steerablesection 68 may be deformed into a curved shape to direct inner probe 74in a transverse direction relative to the straight proximal portion 72,as shown in FIG. 5B. Once in this curved configuration, inner probe 74may be slidably advanced from superior sub-probe 38 as shown in FIG. 5C.

[0139] Referring to FIG. 6, actuator 44D is slidably disposed in alongitudinal slot 132 in handle 42 and is coupled to the proximal end ofinferior sub-probe 40. Actuator 44E is slidably disposed in alongitudinal slot 134 in handle 42 and is coupled to the proximal end oftether 80. When sub-probe 40 is to be deployed, actuator 44D is slidforward, advancing inferior sub-probe 40 distally. Actuator 44E may beallowed to slide forward as well, or it may be held in position tomaintain tension on tether 80, thereby bending sub-probe 40 into thecurved shape shown in FIG. 2E. When sub-probe 40 has been fullyadvanced, actuator 44E may be released, allowing distal end 78 ofsub-probe 40 to engage the pericardial reflection along the inferiorsurfaces of the pulmonary veins, as further described below.

[0140] Actuators 44A-C are slidably disposed in a longitudinal slot 136in handle 42, as more clearly shown in FIG. 7. Actuator 44A is attachedto the proximal end of superior sub-probe 38, and may be advancedforward to deploy the sub-probe from working end 24, as shown in FIG.2A. Actuator 44B is attached to inner probe 74, which is frictionallyretained in inner lumen 96 such that it is drawn forward with superiorsub-probe 38. Actuator 44C is attached to pull wire 126 which is alsodrawn forward with superior sub-probe 38. In order to deflect thesteerable section 68 of superior sub-probe 38, actuator 44C is drawnproximally, tensioning pull wire 126 and bending steerable section 68into the configuration of FIG. 2C. Finally, to deploy inner probe 74,actuator 44B is pushed forward relative to actuators 44A and 44C,advancing inner probe 74 from superior sub-probe 38 as shown in FIG. 2D.

[0141] The slidable relationship between the shafts and probes 74, 40,38 helps to guide and direct the probes to the tissues to be ablated.The shafts have various features, including the ablating elements 27,however, the shafts may be simple sheaths which locate structures and/ordirect the probes into various regions of the pericardial space.

[0142] Referring now to FIGS. 8-11, a preferred embodiment of the methodof the invention will be described. Initially, left ablation probe 20and right ablation probe 22 are connected to an RF generator 140. RFgenerator 140 will preferably provide up to 150 watts of power at about500 kHz, and will have capability for both temperature monitoring andimpedance monitoring. A suitable generator would be, for example, aModel No. EPT-1000 available from the EP Technologies Division of BostonScientific Corp. of Natick, Mass. Retraction, visualization, temperaturemonitoring, suction, irrigation, mapping or ablation devices may beinserted through working port 142. Left ablation probe 20 may further beconnected to a source of suction or inflation fluid 144, for reasonsdescribed below. If electromagnets are provided on left and rightablation probes 20, 22 as described above, an additional connection maybe made to a power supply and switch for operating the electromagnets,or power may be supplied by RF generator 140 through connectors 46, 64.

[0143] A subxiphoid incision (inferior to the xiphoid process of thesternum) is made about 2-5 cm in length. Under direct vision throughsuch incision or by visualization with an endoscope, a second smallincision is made in the pericardium P (FIG. 9). Left ablation probe 20is introduced through these two incisions and advanced around theinferior wall of the heart H to its posterior side under fluoroscopicguidance using fluoroscope 146. Alternative methods of visualizationinclude echocardiography, endoscopy, transillumination, and magneticresonance imaging. Left ablation probe 20 is positioned such that leftinferior pulmonary vein LI is disposed in notch 34 as shown in theposterior view of the heart in FIG. 10.

[0144] Superior sub-probe 38 is then advanced distally from working end24 until its steerable section 68 is beyond the superior side of theleft superior pulmonary vein LS. Steerable section 68 is then deflectedinto the curved configuration shown in FIG. 10 such that its distal end70 is superior to the left superior pulmonary vein LS and pointingrightward toward the right superior pulmonary vein RS. Inner probe 74 isthen advanced toward the right until its distal tip is very close to orcontacting the pericardial reflection PR superior to the right superiorpulmonary vein RS.

[0145] Inferior sub-probe 40 is next advanced from working end 24 whilemaintaining tension on tether 80 such that the inferior sub-probeengages and conforms to the shape of the pericardial reflection PRbetween the left inferior and right inferior pulmonary veins. Wheninferior sub-probe 40 has been fully advanced, tension is released ontether 80 so that distal tip 78 moves superiorly into engagement withthe right inferior pulmonary vein RI adjacent to pericardial reflectionPR inferior thereto.

[0146] Right ablation probe 22 is placed through the subxiphoid incisionand pericardial incision and advanced around the right side of the heartas shown in FIG. 8. Under fluoroscopic guidance, right ablation probe 22is positioned such that cross-member 58 engages the right superior andinferior pulmonary veins, as shown in FIG. 10. In this position,superior tip 106 and inferior tip 124 should be generally in oppositionto distal tip 75 of inner probe 74 and distal tip 78 of inferiorsub-probe 40, respectively, separated by pericardial reflections PR. Inorder to ensure close approximation of the two tip pairs, electromagnets108, 120, 114, 122 may be energized, thereby attracting the tips to eachother across the pericardial reflections RS.

[0147] It should be noted that the pericardium P attaches to the heartat the pericardial reflections PR shown in FIGS. 10- 11. Because of theposterior location of the pulmonary veins and the limited access andvisualization available, cutting or puncturing the pericardialreflections in the vicinity of the pulmonary veins poses a risk ofserious injury to the heart or pulmonary veins themselves. The apparatusand method of the present invention avoid this risk by allowing thepericardial reflections to remain intact, without any cutting orpuncturing thereof, although the pericardial reflections may also be cutwithout departing from the scope of the invention.

[0148] RF generator 140 is then activated to deliver RF energy toelectrodes 28, 60, 66, 76, 82, 104, and 112 on left and right ablationprobes 20, 22, producing the transmural lesion L shown in FIG. 11.Preferably, power in the range of 20-150 watts is delivered at afrequency of about 500 kHz for a duration of about 30-180 seconds,resulting in localized myocardial temperatures in the range of 45-95° C.Ultrasound visualization may be used to detect the length, locationand/or depth of the lesion created. Lesion L forms a continuouselectrically-insulated boundary encircling the pulmonary veins therebyelectrically isolating the pulmonary veins from the myocardium outsideof lesion L.

[0149] Ablation probes 20, 22 may further be used for mapping conductionpathways in the heart (local electrocardiograms) for the diagnosis ofelectrophysiological abnormalities. This is accomplished by selectingany of the electrodes on the ablation probes and monitoring the voltage.A commercially available electrophysiology monitoring system isutilized, which can select any electrode on the ablation probes andmonitor the voltage. Various electrodes and various locations on theheart wall may be selected to develop a map of potential conductionpathways in the heart wall. If ablation treatment is then required, thesteps outlined above may be performed to create transmural lesions atthe desired epicardial locations.

[0150] During any of the preceding steps, devices may be placed throughworking port 142 and working channel 92 to assist and supplement theprocedure. For example, a flexible endoscope may be introduced forvisualization to assist positioning. Ultrasound probes may be introducedto enhance visualization and for measuring the location and/or depth oftransmural lesions. Suction or irrigation devices may be introduced toclear the field and remove fluid and debris. Tissue manipulation andretraction devices may be introduced to move and hold tissue out of theway. Cardiac mapping and ablation devices may also be introduced toidentify conduction pathways and to supplement the ablation performed byleft and right ablation probes 20, 22.

[0151] Furthermore, mapping and ablation catheters, temperaturemonitoring catheters, and other endovascular devices may be used inconjunction with the left and right ablation probes of the invention byintroducing such devices into the right atrium or left atrium eitherthrough the arterial system or through the venous system via the rightatrium and a transeptal puncture. For example, an ablation catheter maybe introduced into the left atrium to ablate any region of themyocardium not sufficiently ablated by left and right ablation probes20, 22 in order to ensure complete isolation of the pulmonary veins.Additionally, ablation catheters may be introduced into the rightchambers of the heart, or epicardial ablation devices may be introducedthrough incisions in the chest, to create other transmural lesions.

[0152] In some cases, it may be desirable to actively ensure adequatecontact between the epicardium and the electrodes of left and rightablation probes 20, 22. For this purpose, left ablation probe 20 and/orright ablation probe 22 may include one or more expandable devices suchas balloons which are inflated in the space between the heart and thepericardium to urge the ablation probe against the epicardial surface.An exemplary embodiment is shown in FIG. 12, in which a balloon 150 ismounted to the outer surface of inner probe 74 opposite electrodes 76 onleft ablation probe 20. Inner probe 74 further includes an inflationlumen 152 in communication with an opening 154 within balloon 150 andextending proximally to inflation fitting 50 on handle 42, through whichan inflation fluid such as liquid saline or gaseous carbon-dioxide maybe delivered. When inflated, balloon 150 engages the inner surface ofthe pericardium P and urges inner probe 74 against the epicardialsurface of heart H. This ensures close contact between electrodes 76 andthe epicardium, and protects extracardiac tissue such as the pericardiumand phrenic nerve from injury caused by the ablation probes. Balloons orother expandable devices may similarly be mounted to superior sub-probe38, inferior sub-probe 40, or right ablation probe 22 to ensuresufficient contact between the epicardium and the electrodes on thosecomponents.

[0153] Alternatively or additionally, suction ports may be provided inthe ablation probes of the invention to draw the electrodes against theepicardium, as shown in FIG. 13. In an exemplary embodiment, suctionports 156 are disposed in inner probe 74 between or adjacent toelectrodes 76. Suction ports 156 are in communication with a suctionlumen 158 which extends proximally to suction fitting 48 on handle 42.In this way, when suction is applied through suction port 156, innerprobe 74 is drawn tightly against the heart, ensuring good contactbetween electrodes 76 and the epicardium. In a similar manner, superiorsubprobe 38, inferior sub-probe 40 and right ablation probe 22 mayinclude suction ports adjacent to the electrodes on those components toenhance contact with the epicardium.

[0154] Referring to FIGS. 14A, 15, 16 and 17, the ablating device 20 isshown with various features described above. The embodiments arespecifically referred to as ablating device 20A and like or similarreference numbers refer to like or similar structure. The ablatingdevice 20A may have any of the features of the ablating devices 20, 22described above and all discussion of the ablating devices 20, 22 or anyother ablating device described herein is incorporated here. Asmentioned above, the ablating device 20A may have a pre-shaped portion160 or a flexible or bendable portion 162 as shown in FIGS. 14 and 15,respectively. A stylet 164 or sheath (not shown) is used to shape theablating device 20A as described below. The stylet 164 passes through aworking channel 166 which may receive other devices as described above.The working channel 166 may also be coupled to a source of fluid 169,such as fluoroscopic contrast, which may be used for visualization. Thecontrast may be any suitable contrast including barium, iodine or evenair. The fluoroscopic contrast may be introduced into the pericardialspace to visualize structures in the pericardial space.

[0155] Referring to FIG. 14A, the pre-shaped portion 160 has a curved orL-shape in an unbiased position. The distal portion of the device 20Amay have any other shape such as a hook or C-shape to pass the device20A around a structure. The stylet 164 holds the pre-shaped portion 160in any other suitable geometry, such as dotted-line 167, forintroduction and advancement of the ablating device 20A. The stylet 164may also be malleable. When the ablating device 20A is at theappropriate position, the stylet 164 is withdrawn thereby allowing thedistal end 160 to regain the angled or curved shape. The device 20A mayalso be shaped with a sheath (not shown) through which the device 20Apasses in a manner similar to the manner of FIGS. 2 and 5.

[0156] Referring to FIG. 15, the ablating device 20A has the flexibledistal portion 162 which is shaped by the stylet 164 into the dottedline 168 position. The pre-shaped portion 160 may be used to position oradvance the ablating device 20A between the epicardium and pericardium.FIG. 18 shows the pre-shaped portion positioned around the left superiorpulmonary vein as described below. A number of different stylets 164 maybe used to shape the flexible portion 162 around various structures.

[0157] The ablating device 20A also has an anchor 170 to anchor aportion of the device 20A while moving another part of the device 20A.When the anchor 170 is the balloon 150, the balloon may have a number ofchambers 171, preferably three, which can be inflated as necessary toposition the device as shown in FIGS. 16 and 17. The chambers 171 arecoupled to a source of inflation fluid 173 via inflation lumens 175. Theanchor 170 is preferably an expandable element 172 such as the balloon150, but may also be tines which grab the epicardium, pericardium orpericardial reflection. The anchor 170 may also be one or more suctionports 156, as described above (see FIG. 13). The suction ports 156 maybe used to anchor the device to the pericardium, epicardium, pericardialreflection or any other structure in the space between the pericardiumand epicardium. Although only one anchor 170 is located at the distalend, the anchor 170 may be positioned at any other location and morethan one anchor 170 may be provided without departing from the scope ofthe invention.

[0158] Referring to FIGS. 18-21, a specific use of the ablating device20A is now described. The ablating devices described herein may, ofcourse, be used to ablate other tissues when positioned in the spacebetween the epicardium and pericardium. The ablating device 20A ispreferably introduced in the same manner as the ablating device 20 or inany other suitable manner. When the ablating device 20A is at theentrance to the transverse pericardial sinus, the ablating device 20Amay be given the angled or curved shape by advancing or withdrawing thestylet 164 (see FIGS. 14 and 15) or with the sheath (see FIGS. 2 and 5).The device 20A is then advanced until the tip meets the pericardialreflection at the end of the sinus as shown in FIG. 18. The anchor 170,such as the balloon 150, is then actuated to resist movement of thedistal end when displacing other parts of the ablating device 20A (FIG.19). At this time, the ablating device 20A may be used to ablate tissuein the manner described above from a position superior to the rightsuperior pulmonary vein, around the left superior pulmonary vein and tothe left inferior pulmonary vein. Thus, the ablating device 20A issimilar to the ablating device 20 described above in that the device 20Aextends through the transverse pericardial sinus and to the leftinferior pulmonary vein.

[0159] The ablating device 20A, like the ablating device 20, may alsohave a portion 176 which is moved to ablate tissue inferior to the leftand right inferior pulmonary veins. Stated another way, the portion 176is moved to a position inferior to the inferior pulmonary veins. Theportion 176 is moved into the position shown in FIG. 20 by simplypushing the device 20A to displace the portion 176 or by advancing orwithdrawing the stylet 164. After the ablating device 20A is properlypositioned, the ablating elements 27 are activated as described above tocreate transmural lesions.

[0160] Still referring to FIG. 20, another ablating device 22A may alsobe used to ablate tissue in the same manner as the ablating device 22described above. The ablating device 22A is introduced in the mannerdescribed above and is advanced until distal end 177 is positioned at adesired location. FIG. 20 shows the distal end 177 superior to the rightsuperior pulmonary vein adjacent to the pericardial reflection. Aportion 179 of the ablating device 20A is then moved to the position ofFIG. 21 in any manner described above such as by introduction orwithdrawal of the stylet 164. The ablating device 20A is then used toablate tissue as described above.

[0161] The ablating device 20A, 22A are also similar to the ablatingdevices 20, 22 in that the ablating devices 20A, 22A create continuouslesions on both sides of the pericardial reflections extending betweenthe vena cava and the right superior and right inferior pulmonary veins.Tissue beneath the pericardial reflections is ablated using at least oneof the ablating devices 20A, 22A. The ablating devices 20A, 22A may beapproximated using any suitable technique or device such as withmagnetic force described above. Other methods and devices for creating acontinuous lesion beneath a pericardial reflection are described below.

[0162] Referring now to FIG. 22, another system and method forapproximating the ablating devices 20, 22 and 20A, 22A is now described.An energy emitter 180, such as a light source 182, emits energy from theablating device 20A which is received by a sensor 184 on the otherablating device 22A to determine when the devices 20A, 22A arepositioned on opposite sides of a pericardial reflection. The emitter180 and sensor 184 preferably pass through the working channel 166 butmay also be integrated into the devices 20A, 22A. When the ablatingdevices 20A, 22A are aligned across the pericardial reflection, thesensor 184 detects proper alignment so that the lesion may be formedcontinuously on both sides of the pericardial reflection.

[0163] Yet another method to make sure that the ablating devices 20A,22A are aligned across a pericardial reflection is to mark a location onthe pericardial reflection where a lesion has been created as shown inFIG. 23. The device 20A has a needle 185 introduced through the workingchannel 166. The needle 185 delivers a marker 186, such as a radioopaquedye, which can be visualized. The device 20A may also deliver a solidmarker such as a platinum wire. An advantage of using the marker 186 isthat both ablating devices 20A, 22A do not need to be positioned onopposite sides of the pericardial reflection at the same time. Thus,only one ablating device 20A may be necessary to create a continuouslesion beneath the pericardial reflection since the same device 20A canmark the pericardial reflection on one side, locate the mark 186 on theother side, and continue the lesion on the other side of the pericardialreflection.

[0164] Referring again to FIG. 10, the ablating device 20 has the guideportion 25. As mentioned above, the guide portion 25 preferably has awidth to height ratio of about 2 to 5. The guide portion 25 aligns theablating element 27 against a predetermined structure, such as thepulmonary veins, to ablate tissue. The relatively flat configuration ofthe guide portion 25 aligns the device 20 between the epicardium and thepericardium so that the ablating elements 27 are directed toward themyocardium.

[0165] Referring now to FIG. 24, an ablating device 20B is shown whichhas a number of discrete guide portions 25A. Four guide portions 25A areshown in FIG. 24 with each guide portion 25A being shaped similar to afin 29. The ablating device 20A may also have a beaded or scallopedappearance. The ablating device 20A preferably has flexible sections 188between the guide portions 25A which provide torsional flexibility sothat the guide portions 25A can rotate relative to one another. Theguide portions 25A may be positioned between the pulmonary veins asshown in FIG. 27A. The ablating device 20B may have any of the featuresof the other ablating devices 20, 20A described herein.

[0166] Referring to FIG. 25, another ablating device 20C is shown whichhas guide portions 25B which may also be deployed after the ablatingdevice 20C has been positioned so that the guide portion 25B does notinterfere with advancement and placement. The guide portion 25B has oneor more expanding elements 192, such as the balloons 150, which may beexpanded during advancement or after the device 20A is at the desiredlocation. The expanding elements 192 are positioned on opposite sides ofthe ablating device 20C, however, the expanding elements 192 may bepositioned only on one side of the device 20C. The guide portions 25Amay be positioned between the pulmonary veins as shown in FIG. 27B. Theexpanding elements 192 may also be mechanically actuated elements suchas bending arms or an expandable mesh.

[0167] The expanding elements 192 may also be inflated at selectedlocations corresponding to discrete ablation sites as shown in FIG. 26.An advantage of individual expansion of the expanding elements 192 isthat other portions of the device 20C may rotate and displace asnecessary to provide good contact at the desired ablation site 193.

[0168] Another ablating device 20D is now described with reference toFIGS. 28-31. The ablating device 20D is advanced over a guide 200 whichis advanced ahead of the device 199. The guide 200 is preferably aguidewire 202 having the anchor 170 to anchor an end 204 of the guide200. The guide 200 is advanced and positioned along the intendedablation path. The ablating device 20D is then retracted or advancedalong the guide 200 to create a continuous lesion along the intendedablation path. The guide 200 may also be locked into a desiredorientation with a coaxial cable or with a mechanism similar to lockingarms used to hold surgical devices. The ablating device 20D has anexpanding device 201, such as the balloon 150, to move the ablatingelement 27 into contact with the tissue to be ablated. The balloon 150preferably has a number of chambers 203, preferably at least two,coupled to inflation lumens 205, 207 which are coupled to the source ofinflation fluid 173 (FIG. 14A). Electrodes 191, 193 are coupled to wires209, 211 passing through the device 20D. The guide 200 passes throughthe working channel 166. Wires 213 are also provided to steer, rotateand position the device 20D.

[0169] The ablating device 20D and/or the guide 200 preferably includesa device 206 for aligning the ablating element with a previously createdlesion. The aligning device 206 may be electrodes 191, 193 which simplymeasure electrical impedance. When the electrodes 191, 193 measure alarge increase in electrical impedance an ablation is positioned beneaththe electrodes 191, 193. In this manner, the ablating element 27 can bealigned and positioned to create a continuous lesion through the tissue.Referring to FIG. 29, the electrodes 191, 193 may also be used to locatethe previously created lesion 195 as shown in FIG. 29. The electrode 191will sense a higher amplitude of activity than the electrode 193 sincethe electrode is positioned over the previously created lesion while theelectrode 191 is not.

[0170] Still referring to FIG. 28, the ablating device 20D may havefirst and second electrodes 194, 196 on opposite sides of the ablatingelement 27. The first electrode 194 may be a pacing electrode 195 whichemits an electrical impulse and the second electrode 196 may be asensing electrode 197 which receives electrical impulses. When the firstelectrode 194 emits a stimulus, launching a cardiac impulse, the impulseis transmitted through tissue to the sensing electrode 197 if adiscontinuity exists in the lesion. A number of sensing electrodes 197may be positioned along the ablating device 20A which may be used todetermine the location of a discontinuity. Both electrodes 194, 196 mayalso be sensing electrodes 197 with both electrodes 194, 196 merelysensing normal activity. When only one of the electrodes 194, 196 sensesthe activity an effective, continuous, transmural lesion has beencreated. The electrodes described herein may be coupled to any suitabledevice including an ECG with electrogram amplitudes being measured.

[0171] The electrodes 194, 196 may also be used to locate the end of apreviously created lesion. The time between emission of the pacingstimulus to receipt of the cardiac impulse at the sensing electrodeincreases when a transmural ablation has been created between theelectrodes 194, 196. When such an increase is detected, it is known thatthe previously created lesion is positioned between the electrodes 194,196. The time between emission and receipt of the cardiac impulse mayalso be used in simple time of flight analysis to determine the locationof a discontinuity in the ablation. For example, the electrodes 194, 196are positioned at a discontinuity in an ablation when the time of flightis lowest.

[0172] A method of using the device is shown in FIGS. 32-35. The guide200 is advanced to a desired location and the anchor 170 is actuated.The ablating device 20D is then advanced over the guide 200, the balloon150 is inflated, and a first ablation 215 is performed. The balloon 150is then deflated and the ablating device 20C is then moved to anotherlocation. The electrodes 191, 193 or 194, 196, or other suitablealigning device, is used to position and align the ablating device 20Dand a second ablation 217 is then performed which is continuous with thefirst ablation 215. The device 20D is then moved again and a thirdablation 219 is formed continuous with the second ablation 217.

[0173] Referring to FIGS. 36-38, another ablating device 210 is shownwherein the same or similar reference numbers refer to the same orsimilar structure. The ablating device 210 has an expandable structure209, preferably a balloon 150A, movable along the ablating device 210 toselectively anchor and align the device 210. An advantage of the systemof FIGS. 36-38 is that the structure 209 can be moved to variouslocations on the ablating device 210 for moving various ablatingelements into contact with tissue to be ablated. The ablating device 210also has the anchor 170, such as the balloon 150B, to anchor a part ofthe ablating device 210 and to move the ablating elements 27 intocontact with the tissue to be ablated. The balloon 150B is coupled to asource of inflation fluid 211 via inflation lumen 223.

[0174] The expandable device 209 is mounted to a body 211 having ascalloped appearance to provide flexibility although any other suitabledesign may be used. The body 211 has a C-shaped cross-section whichengages a flange 221 on the ablating device 210. The expandable device209 is preferably the balloon 150A but may be a mechanically actuateddevice. For example, the expandable device 209 can be an extendable arm,a wire loop or an expandable mesh. The anchor 170 may be selectivelyexpandable to guide, rotate, and move the ablating device 210 asnecessary. The balloon 150A preferably has at least two separatelyinflatable chambers 212 and FIG. 38 shows the balloon 150A having threeindependently inflatable chambers 212. The chambers 212 are coupled toinflation lumens 219 which are coupled to a source of inflation fluid213. The chambers 212 may be inflated as necessary to move and rotatethe ablating device 210 and press the ablating element 27 against thetissue to be ablated. The expandable structure 209 is moved to variouspositions along the ablating device 210 to move various ablatingelements 27 into contact with the tissue. The body 211 may also havepull wires 218 for further manipulation of the ablating device 210.

[0175] As mentioned above, penetrating the pericardial reflectionscarries inherent risks. However, the methods and devices of theinvention may, of course, be used when penetrating the pericardialreflections. The ablating devices 20, 22, 20A, 22A may have apenetrating element 220 as shown in FIGS. 39-43 for penetrating thepericardial reflections. The penetrating element 220 is movable from aretracted position (FIG. 40) to an extended position (FIG. 41). Thepenetrating element 220 passes through the working channel 166 of theablating device 20A. The penetrating element 220 is preferablypositioned in the working channel 166 but may also be integrated intothe ablating device 20A or may be a separate device altogether. Thefirst and second ablating devices 20A, 22A are positioned on oppositesides of the pericardial reflection as shown in FIG. 40 using theemitter and sensor arrangement described above in connection with FIG.22 although any other devices or techniques may be used. The penetratingelement 220 is then used to penetrate the pericardial reflection and thetwo devices 20A, 22A are interlocked as shown in FIGS. 41.

[0176] Referring to FIGS. 42 and 43, the ablating device 22A has alocking mechanism 224 which holds the penetrating element 220. Thelocking mechanism 224 has a stationary jaw 230 and a movable jaw 231.The movable jaw 231 is movable in the direction of arrow 223 forreleasing the device 20A. The locking mechanism 224 is also positionedin the working channel 166 of the ablating device 22A but may beintegral with the device 22A. The penetrating element 220 preferably hasa conical tip 222 or other cutting element for piercing the pericardialreflection but may also be a laser, ultrasonic dissector, orelectrosurgical device. The penetrating element 220 may also be a blade,needle or other structure for cutting or piercing the pericardialreflection. After ablating tissue, the locking mechanism 224 isreleased, the penetrating element 220 is retracted and the ablatingdevices 20A, 22A are removed. The ablating devices 20A, 22A may have anyother interlocking configuration and the ablating device 22A mayinterlock with some other structure other than the penetrating element220. Referring to FIG. 48, the ablating devices 20, 22 may interlockwith one another in the manner described above. Referring to FIG. 44,the ablating device 20 may penetrate through one or more pericardialreflections and interlock with another part of the ablating device 20.Referring to FIG. 45, the ablating device 20 and the ablating device 22may also interlock across the pericardial reflections using thepenetrating element 220 or other suitable device.

[0177] Referring to FIGS. 46-49, another method of penetrating andadvancing through the pericardial reflection is shown. The end of theablating device 20A may be adhered to the pericardial reflection usingsuction through the working channel 166. The penetrating element 220 isthen advanced through the working channel 166 while suction ismaintained so that the piercing element is guided directly to thepericardial reflection. The penetrating element 220 is then used topenetrate the pericardial reflection as shown in FIG. 45. The ablatingdevice 20A is then advanced through the pericardial reflection as shownin FIG. 46.

[0178] Referring to FIG. 14B, another anchor 170A for anchoring thedevice is shown. Any of the anchors described herein may be used withany of the devices described herein without departing from the scope ofthe invention. The anchor 170A is a relatively flat balloon having athickness of about 1 cm and a width of about 0.3 cm when the balloon isinflated. Referring to FIG. 14C, yet another inflatable anchor 170B isshown which forms a hook-shaped element 171 which can engage a vesselsuch as the aorta, superior or inferior vena cava or any other vesselmentioned herein. Referring to FIG. 14D, still another anchor 170C isshown which has a mechanically expanding coiled section 173. Asmentioned above, the anchors of the present invention are expanded tohold the devices at a particular location. For example, the anchors maybe used to anchor a part of the device between blood vessels such as thesuperior vena cava and the aorta. When positioned between blood vesselsor when engaging a vessel with the hook-shaped element of FIG. 14C,tension may be applied to the device to wrap the device around a vesselor vessels, such as the pulmonary veins, in the manner described above.

[0179] Referring to FIG. 49-54, another device 300 for ablating tissue,such as cardiac tissue, is shown. The device 300 may also be used in anymanner described herein and may have the features and dimensions ofother devices described herein without departing from the scope of theinvention. The device 300 encircles the pulmonary veins and isparticularly suited for conventional open chest surgery but may also beused in less and minimally invasive procedures. Although ablation oftissue around the pulmonary veins is described as a specific use of thedevice 300, the device 300 may be used on other parts of the heart andin other areas of the body.

[0180] The device 300 has a body 302 having a length of 5-12 inches,preferably about 10 inches, and a width of 0.2-0.7 inch preferably about0.5 inch. The body 302 is preferably made of an polymeric material suchas silicone or urethane and is formed by injection molding although anysuitable material and method may be used to form the body 302. The body302 has a number of cells 304 coupled together by integrally formedhinges 303 in the body 302. Of course, the cells 304 may be coupledtogether with mechanical connections rather than the integrally formedhinges 303 without departing from the scope of the invention. The device300 preferably has 5-30 cells, more preferably 10-25 cells and mostpreferably about 16 cells although any number of cells 304 may be useddepending upon the specific application. For example, the device 300 maybe used to extend around a single vessel, such as the aorta, pulmonaryvein, SVC or IVC in which case the device 300 preferably has 4-12 cells304 and preferably about 8 cells 304.

[0181] The device 300 has a locking mechanism 306, preferably a buckle308, which engages another part of the device 300 to form a closed loop307. Referring to FIG. 49, the device 300 extends around the pulmonaryveins with the locking mechanism 306 to form the closed loop 307 aroundthe pulmonary veins. The buckle 308 forms a side-by-side (FIG. 50) orone on top of the other (FIG. 51) locking engagement with another partof the device 300. Although the buckle 308 is preferred, the lockingmechanism 306 may have any other suitable structure for locking one partof the device 300 to another part of the device 300.

[0182] Referring now to FIGS. 49, 52, 53A and 54, the cells 304 have asuction well 310 for adhering the device to the tissue to be ablated.The suction well 310 may take any form and is preferably formed betweenan inner lip 312 and an outer lip 314. The suction well 310 has asuction port 316 coupled to a vacuum source 318 through a lumen 320. Thevacuum source 318 is activated to cause the suction well 310 to hold thecell 304 against the tissue to be ablated. The lumen 320 is preferablyformed by a separate tube 322 bonded to the body 302. The lumen 320 may,of course, be formed integral with the rest of the body 302. The uppersurface of the cells 304 has three longitudinal recesses 324 in whichthe tubes 322, 326, 328 are positioned. The tubes 322, 326, 328 haveslack between the cells 304 to permit the cells 304 to wrap aroundstructures without significant resistance from the tubes 322, 326, 328.

[0183] The suction port 316 preferably has a cross-sectional size whichis no more than 10% of the cross-sectional size of the lumen 320. Inthis manner, if suction is lost at one of the cells 304, suction can bemaintained at the other cells 304 since the relatively small suctionport 316 produces low flow. Of course, another part of the vacuum flowpath 317 other than the suction port 316 may be sized small to reducelosses through cells 304 not adhered to the tissue.

[0184] An ablating element 311 is positioned within a closed wall 319formed by the inner lip 312 so that the ablating element 311 issurrounded by the suction well 310. The ablating element 311 may be anyablating element mentioned herein and a preferred element is an RFelectrode 330. The RF electrode 330 is coupled to an RF generator 332which transmits RF energy to the electrode. The RF electrode 330 ispreferably a stainless steel or gold plated copper electrode althoughany suitable electrode may be used. The ablating element 311 preferablyhas a width of 1-6 mm, preferably about 3 mm, and a length of 2-25 mm,preferably about 12 mm. When the ablating element 311 is the RFelectrode, the ablating element 311 is preferably spaced apart from thetarget tissue, or from a bottom of the inner lip 312, by a distance of0.5-3 mm and more preferably about 1.5 mm. The locking mechanism 306preferably has at least one ablating element 311 to create a continuouslesion in tissue beneath the locking mechanism 306.

[0185] The ablating elements 311 are coupled to a control system 334with wires 345. The control system 334 controls ablation in the mannerdescribed below. The RF generator 332 may form part of the controlsystem 334 or may be separate from the control system 334. One or moretemperature sensors 336, preferably thermocouples 338, are positionedwithin recesses in the inner and/or outer lips 312, 314 to measuretemperature. The temperature sensors 336 are coupled to the controlsystem 334 for use as described below. Wires 340 extending through thetube 326 couple the temperature sensors 336 to the control system 334.

[0186] Fluid is delivered to cool the tissue and/or conduct energy fromthe ablating element 311 to the tissue. Fluid is supplied from a sourceof fluid 342 to an inlet lumen 344 formed by tube 328. Fluid iswithdrawn through the lumen 320 in the tube 322 so that the lumen 320produces suction at the suction well 310 and withdraws fluid. Asmentioned above, the lumens 344, 346 are preferably formed by the tubes322, 328 but may be integrally formed with the rest of the body 302. Thefluid is preferably a conductive solution, such as saline or hypertonicsaline, which conducts RF energy from the electrode 330 to the tissue tobe ablated.

[0187] Referring to FIGS. 53A and 54, fluid flows from the inlet lumen344 into an inlet manifold 350 which distributes fluid along the lengthof the ablating element 311 as shown in the cross-sectional view of FIG.54. Fluid then flows into a fluid chamber 348 formed between theablating element 311, inner lip 312 and tissue. Fluid passes across thefluid chamber 348 and is received at a fluid outlet manifold 352. Thefluid outlet manifold 352 is coupled to the lumen 320 so that the lumen320 withdraws fluid and provides suction for the suction well 310 asmentioned above.

[0188] The fluid inlet and outlet 350, 352 are preferably positioned onopposite sides of the short axis of the fluid chamber 348, however, thefluid inlet and fluid outlet 350, 352 may be positioned anywhere withinthe fluid chamber 348 without departing from the scope of the invention.Fluid is preferably supplied at an average flow rate of at least 0.24cc/sec, more preferably at least 0.50 cc/sec and most preferably atleast 1.0 cc/sec to each cell 304 although lower or higher flows may beused. Fluid is preferably delivered to the inlet lumen 344 at a setpressure which results in the desired average flow rate through thecells 304. The fluid may be cooled, or even heated, by passing the fluidthrough a heat exchanger 354. The fluid is preferably delivered at atemperature of no more than 40° C. and more preferably no more than 20°C. to cool the tissue and/or ablating element 311. A fluid permeable,porous structure, such as gauze (not shown), may be positioned in thefluid chamber 348 to hold the fluid and prevent direct contact betweenthe ablating element 311 and tissue.

[0189] Referring to FIG. 53B, the device 300E may also provide coolingto a backside 353 of the ablating element 311. Fluid from the inletlumen 344 passes across the backside 353 of the ablating element 311 andis removed on the other side through the lumen 320. The embodiment ofFIG. 53B may include any of the features and advantages of theembodiment of FIG. 35, for example, the fluid flow rate and temperaturemay be the same as described in relation to FIG. 53A. The inlet lumen344 is also coupled to the suction well 310 via a conduit 355 forsupplying fluid to the suction well 310. In this manner, the fluid mayalso be used to cool tissue adjacent to the ablating element 311. Fluidintroduced into the suction well 310 is withdrawn through the lumen 320in the manner described above. Although the fluid in the suction well310 is exposed to the near surface NS of the tissue, the cooling fluidmay also be contained within a closed circuit so that the near surfaceNS of the tissue is not in direct contact with the fluid. Furthermore,the fluid preferably cools tissue around the entire ablating element 311but may also cool tissue only along one side of the device or only onthe two lateral sides of the device without departing from the scope ofthe invention.

[0190] Referring to FIGS. 55 and 56, another device 300E is shown wherethe same or similar reference numbers refer to the same or similarstructure. Use and dimensions of the device 300 are equally applicablefor the device 300E. The device 300E has a lumen 356 contained within acavity 358 in the body 302E. The lumen 356 carries the wires 340, 345for the temperature sensors 336 and ablating elements 311. The lumen 356is coupled to the control system 334 for control in the manner describedbelow. The lumen 346 is a dedicated lumen for withdrawing fluid so thatthe fluid can be recycled as shown in FIG. 56. The system of FIG. 56 isdescribed in greater detail below in connection with use of the devices300, 300E. The lumen 356, wires 340, 345, ablating elements 311, andtemperature sensors 336 form a strip 359 which is bonded to the rest ofthe body 302, preferably with an interlocking engagement.

[0191] A pair of wires 360, 362 is positioned across a gap 361 insuction path 363 (shown in dotted-line) to determine when the inner lip312 is not adequately adhered to the tissue. When the inner lip 312 isnot adequately adhered to the tissue, fluid leaks under the inner lip312 and is drawn into the vacuum outlet 316. The fluid, which ispreferably cooled hypertonic saline, conducts electricity across the gap361 thereby indicating that the inner lip 312 may not be adequatelysealed. The wires 360, 362 may be embedded in the body 302E or maytravel through one or more of the lumens.

[0192] Referring to FIG. 57, another device 300F is shown which has twosets of lumens 364, 368 extending from both ends of the device 300F. Thetwo sets of lumens 364, 368 perform the same functions as the lumensdescribed above and all discussion of the device 300 is equallyapplicable here. An advantage of using two sets of lumens 364, 368 isthat suction and/or fluid containment does not need to be maintained atall cells 304 at the same time. Connectors 370 at the buckle 308 aredisconnected to wrap the device 300F around the pulmonary veins and arethen reconnected to form the closed loop. Each set of lumens 364, 368terminates near the middle of the device 300F at ends 372. Valves 374are provided to selectively couple the lumens 362, 368 to the vacuumsource 318 and/or fluid supply 342.

[0193] Referring to FIGS. 49 and 52-57 the control system 334 is coupledto the temperature sensors 336, ablating elements 311, fluid source 342and vacuum source 318 for controlling the devices 300, 300E, 300F. Thecontrol system 334 may also be coupled to a pressure sensor 376 and/or aflow rate sensor 378 positioned along the inlet line of the vacuumsource 318 (FIGS. 56 and 57). The pressure and/or flow rate sensors 376,378 determine when the cells 304 are adequately secured to the tissue.If suction is not adequate, the pressure and/or flow rate will be higherthan expected. Fluid flow indicators 380 can also be used to measurefluid flow into and out of the devices 300E, 300F to determine whetherfluid is leaking from the cells 304 which also indicates a poor seal.

[0194] The cells 304 are preferably numbered and the control system 334indicates whether each cell 304 is adequately adhered to the tissue. Inthis manner, the user may apply manual pressure to a particular cell 304if an adequate seal is not present. The readout may be a digital readout377 or lights 379 for each cell 304. The control system 334 alsopreferably has a temperature display 335 and a timer 337 for timing theduration of ablation.

[0195] The control system 334 preferably activates the ablating elements311 in a predetermined manner. In one mode of operation, ablation iscarried out at adjacent cells 304. Ablation may also be carried out at anumber of pairs of adjacent cells such as the first and second cells 304and the fifth and sixth cells 304. After ablation is carried out atthese adjacent cells 304, another pair or pairs of adjacent cells areactivated such as the third and fourth cells 304 and the seventh andeighth cells 304. The continuity of the ablation between the adjacentcells 304 may be confirmed in any suitable manner including thosedescribed herein. In another mode of operation, the control system 334energizes every other cell, every third cell or a limited number ofcells 304 such as no more than four. The control system 334 may alsoactivate less than 50% and even less than 30% of the total ablation areaat one time. For the device 300, a percentage of the total ablation areais essentially a percentage of the total number of ablation elements311.

[0196] The ablation at each cell 304 may be controlled based ontemperature measured at the temperature sensors 336. For example, thecontrol system 334 may be configured to maintain a near surface NStemperature of 0-80° C., more preferably 20-80° C. and most preferably40-80° C. The temperature can be adjusted by changing the fluid flowrate and temperature and/or the power delivered to the ablating element311. The control system 334 may also have a multiplexer 333 whichdelivers energy to only the cells 304 having a temperature below thethreshold temperature. Alternatively, the multiplexer 333 may deliverenergy to only the coldest cells 304 or only a number of cells 304 whichregister the coolest temperatures.

[0197] The control system 334 may also be configured to measure atemperature response of the tissue to be ablated. The temperatureresponse of the tissue is measured to provide a tissue characterizationwhich can be used to select the appropriate ablation technique. Theablation technique is primarily selected to produce a temperature of atleast 50° C. at the far surface FS of the tissue. When ablating cardiactissue, for example, the control system 334 determines the ablationtechnique required to form a transmural lesion which requires a farsurface FS temperature of 50-80° C. and more preferably 50-60° C.Measuring temperature at the far surface FS is somewhat difficult so thetemperature of the near surface NS is used in conjunction with themethods and devices described herein. Of course, the temperature of thefar surface FS may be measured to determine when the ablation iscomplete rather than using the temperature response described below.

[0198] The temperature response of the tissue is performed in thefollowing manner. The tissue to be ablated is heated or cooled and thetemperature response over time is measured with the temperature sensors336. The temperature response over time at the near surface NS providesa rough indication of the thermal properties of the tissue to beablated. The thermal properties of the tissue is affected by a number ofvariables including tissue thickness, amount of fat and muscle, bloodflow through the region and blood flow and temperature at the farsurface FS. These factors all play a role in the temperature response ofthe tissue. The tissue thickness, for example, affects the temperatureresponse in the following manner. When a thin tissue layer is heated,the temperature at the near surface will generally increase more slowlythan with a thick layer since the flow of blood at the far surface willdraw heat away quicker with the thin tissue layer. The control systempreferably measures the temperature response for at least twotemperature sensors 336 for each ablating element with one of thetemperature sensors being positioned laterally spaced to measure thetemperature change at adjacent portions of the tissue.

[0199] After measuring the temperature change over time, the temperatureresponse is then analyzed to determine the appropriate ablationtechnique. The analysis may be a comparison of the temperature responsewith temperature response curves of known tissue types. The temperatureresponse curves may be developed empirically or may be calculated. Thetemperature response may also consider other variables input by the userincluding blood temperature and flow rate and the presence and amount offat. When assessing the temperature response during heating with theablating element, the amount of energy delivered to the tissue may alsobe used to characterize the tissue.

[0200] Using the results of the temperature response assessment, thecontrol system 334 determines the appropriate ablation technique toproduce the desired far surface FS temperature. In one mode ofoperation, the control system 334 determines the amount of time requiredto reach a desired far surface FS temperature when the near surface NSis maintained at a temperature of less than 60° C. The control system334 preferably maintains an adequate flowrate and temperature of fluidto maintain the desired near surface NS temperature. The control system334 monitors the temperature of the near surface NS with temperaturesensors 336. After the period of time has elapsed, the control system334 automatically stops ablating. Alternatively, the ablation may takeplace until the near surface NS reaches a target temperature. Thecontinuity of the ablation may then be checked in any manner describedherein.

[0201] In use, the devices 300, 300E, 300F are wrapped around astructure, such as the pulmonary veins, with the locking mechanism 306to form the closed loop 307. The vacuum source 318 is then activated toadhere the cells 304 to the epicardium. Manual pressure can be appliedto cells 304 which are not sufficiently adhered to the tissue. Thecontrol system 334 then ablates tissue while delivering fluid to coolthe tissue and conduct RF energy to the tissue. The continuity ofablation is then assessed by any suitable method including thosedescribed herein.

[0202] Referring to FIG. 58-63, still another device 400 is shown forablating tissue wherein the same or similar reference numbers refer tothe same or similar structure. The device 400 is particularly useful forablating cardiac tissue but may be used for any other purpose withoutdeparting from various aspects of the invention. In a specificembodiment, the device 400 is used to ablate tissue around the pulmonaryveins. The ablating device 400 has a number of cells 402 similar to thecells described above and description of the preferred characteristicsabove are equally applicable here. For example, the cells 402 may havethe preferred dimensions and features of the cells 304 described above.The ablating device 400 has an ablating element 404 which is preferablyan ultrasonic transducer 406 although various features of the inventionmay be practiced with any other type of ablating element 464 (FIG. 68).

[0203] The device 400 preferably delivers ultrasound which is focused inat least one dimension. In particular, the device 400 preferablydelivers focused ultrasound having a focal length of about 2 to 20 mm,more preferably about 2 to 12 mm and most preferably about 8 mm. Statedanother way, a focal axis FA is spaced apart from a bottom or contactsurface 405 of the device within the stated ranges. The focusedultrasound also forms an angle of 10 to 170 degrees, more preferably 30to 90 degrees and most preferably about 60 degrees as defined relativeto the focal axis A. The ultrasonic transducer 406 is preferably apiezoelectric element 408. The transducer 406 is mounted within ahousing 410. The housing 410 has an enclosure 412 and a top 414 whichfits over the enclosure 412. The enclosure 412 has curved lips 416 onboth sides of the enclosure 412 which generally conform to the curvatureof the transducer 406. The transducer 406 is curved to focus theultrasound energy for the reasons discussed below. The transducer 406has a length of about 0.43 inch, a width of about 0.35 inch and athickness of about 0.017 inch. The transducer 406 has a radius ofcurvature R (FIG. 62) consistent with the preferred focal lengthsdescribed above. The transducer 406 forms an angle A with the focus Fwithin the preferred angle ranges described above.

[0204] A layer 418, which is preferably aluminum but may be any othersuitable material, is bonded or otherwise acoustically coupled to aconcave side 423 of the transducer 406. The layer 418 has a length ofabout 0.51 inch, a width of about 0.43 inch and a thickness of about0.012 inch. The layer 418 preferably has the same radius of curvature asthe transducer 406 so that the layer 418 mates with the transducer 406.The layer 418 is attached to the curved lips 416 of the enclosure 412with an epoxy.

[0205] An advantage of using focused ultrasonic energy is that theenergy can be concentrated within the tissue. Another advantage of usingfocused ultrasound is that the energy diverges after reaching the focusthereby reducing the possibility of damaging tissue beyond the targettissue as compared to collimated ultrasonic energy. When ablatingepicardial tissue with collimated ultrasound, the collimated ultrasoundenergy not absorbed by the target tissue travels through the heartchamber and remains concentrated on a relatively small area when itreaches the endocardial surface on the other side of the chamber. Thepresent invention reduces the likelihood of damage to other structuressince the ultrasonic energy diverges beyond the focus and is spread overa larger area.

[0206] Although the focused ultrasonic energy is preferably producedwith the curved transducer 406 and the layer 418, the focused ultrasonicenergy may be produced with any suitable structure. For example,acoustic lensing may be used to provide focused ultrasound. The acousticlens can be used with a flat piezoelectric element and matching layer.Furthermore, although the ultrasound energy is preferably emitteddirectly toward the tissue the ultrasound energy may also be reflectedoff a surface and directed toward the tissue without departing from thescope of the invention. The energy may also be produced by a number ofsmall transducers which are oriented to focus or concentrate ultrasonicenergy, such as at least 90% of the energy, within the preferred angleranges and radius of curvature described herein when viewed along alongitudinal axis 419 or along the focal axis FA. For example, amultielement acoustic phased array may be used to provide an acousticbeam-steering capability from one or more cells. One skilled in the artcan also appreciate the use of multiple matching layers, focusingacoustic lenses and non-focusing acoustic windows and the like. Thus,the focused energy may be produced in a number of different ways,including other ways not mentioned here, without departing from thescope of the invention.

[0207] A distributing element 420 is attached to the transducer 406 attwo locations to distribute energy that drives the transducer 406. Theelement 420 is preferably a piece of copper ribbon 0.020 inch wide and0.0005 inch thick soldered to the transducer 406 at two locations. Acoaxial cable 422 delivers power to the transducer 406 from a source ofpower 421 and also provides a ground path. The coaxial cable 422 has apower lead 424 coupled to the distributing element 420 to power thetransducer 406. A braided portion 426 of the cable 422 serves as aground. The braided portion 426 is soldered to a tube 428 and/or the top414. The ground path leads from the transducer 406 to the layer 418 andthen to the housing 410 at the curved lips 416. The ground path thenpasses to the top 414 and finally to the braided portion 426 eitherdirectly or via the tube 428. The tube 428 and top 414 are preferablymade of brass and the enclosure 412 is preferably made of aluminumalthough any other suitable materials may be used. Polyimide tape 430 isadhered to the inside of the enclosure 412 and on the transducer 406 toelectrically separate the two structures.

[0208] The transducer 406 may be cooled during operation althoughcooling may not be required. A cooling inlet 432 having an inlet lumen440 extends through the top 414 and is coupled to a source of coolingmedium 434. The cooling medium, which is preferably forced air, passesinto a chamber 436 so that the cooling medium is in direct contact withthe transducer 406. A cooling outlet 438 having an outlet lumen 442removes the cooling medium from the chamber 436. Although the lumens440, 442 are preferably separate and independent from the housing 420,the lumens 440, 442 may also be integrated into the housing 420 withoutdeparting from the scope of the invention.

[0209] The cells 402 may also be adhered or acoustically coupled to thetissue with suction in the manner described above although variousfeatures of the invention may be practiced without using suction. Thehousing 410 is mounted within an opening 446 in a suction body 448. Thebody 448 has a port 449 coupled to a lumen 452 leading to the vacuumsource 318. The lumen 452 is coupled to the outlet lumen 442 with tubing443 so that the outlet lumen 442 provides suction and withdraws thecooling medium (FIG. 59). Of course, the lumen 452 may also becompletely independent of the outlet lumen 442. FIG. 58 shows separatecooling outlet and vacuum lumens. The port 450 leads to recesses 454 ontwo sides of the transducer 406. The recesses 454 also may be formed byindividual suction pods, a linear segment, or any other suitablestructure without departing from the scope of the invention. A channel456 extends from one side of the enclosure 412 to provide communicationbetween the two recesses 454. The channel 456 prevents only one recess454 from being adhered to the tissue. The body 448 is preferably made ofpolycarbonate but may be made of any other suitable material.

[0210] The ablating device 400 may also be used with a substance, suchas a gel or saline, applied to the target tissue to eliminate air gapsbetween the transducer 406 and target tissue. Air gaps between thetransducer 406 and target tissue impede delivery of ultrasonic energy tothe tissue. When using suction as described below, use of the substancemay be unnecessary since the transducer 406 assembly can be forced intointimate contact with the target tissue with the suction force.

[0211] The ablating device 400 may also have a membrane 460 (FIG. 64)filled with the substance 458 or a solid element 459 (FIG. 65) whichtransmits the ultrasonic energy to the tissue. An advantage of themembrane 460 is that the membrane 460 may be made flexible and compliantto conform to the tissue. Another advantage of the membrane 460 is thatthe distance between the transducer 406 and the tissue may be varied.When ablating thick tissue, the membrane 460 can be deflated so that thetransducer 406 is close to the tissue (FIG. 64). When ablating thintissue, the membrane 460 is inflated so that the transducer 406 isfurther from the tissue (FIG. 66). Adjacent cells preferably maintaincontact with the tissue to maintain the orientation of the device. Themembrane 460 may also be inflated and deflated during or betweenactivations of the transducer 406 to move the focus relative to thetissue. For example, the membrane 460 may be inflated and deflated tomove the focus relative to the tissue and, in particular, to differentdepths. The membrane 460 is adhered to the device around the bottom ofthe enclosure 412. The membrane 460 is preferably compliant and may bemade of any suitable material such as silicone or urethane. The membrane460 may be pre-filled with the substance or the substance may be addedlater through another lumen (not shown).

[0212] Referring to FIG. 67, the membrane 460 may also take a shapewhich tilts the transducer 406. The transducer 406 is preferably tiltedto direct the ultrasound energy to tissue positioned beneath gapsbetween adjacent transducers 406 as will be explained in greater detailbelow. A flexible flange 461 deflects to permit tilting of the device.The transducer 406 may be angled, pivoted or tilted in any othersuitable manner. For example, the transducer 406 may have a mechanicalpivot which moves the transducer 406 or a movable foot on the bottom ofthe device 400 which is advanced and retracted to tilt the transducer406.

[0213] Referring to FIG. 68, another device 462 for ablating tissue isshown wherein the same or similar reference numbers refers to the sameor similar structure. The device 462 has the ablating element 404 whichis preferably an ultrasonic transducer 463. The transducer 463 isdesigned to deliver ultrasonic energy to tissue beneath the transducer463 and to tissue beneath the gaps between adjacent cells 402. In thismanner, the device may be operated without moving or tilting thetransducers 463 to create a continuous lesion beneath the device. Thetransducer 463 is a flat transducer 463 with a layer 464 attachedthereto. The layer has a flat bottom portion 466 and angled sides 468which direct energy at tissue lying beneath the gaps between adjacenttransducers 463. The device 462 has a membrane 470 adhered over thebottom of the cell 402. The membrane 460 is filled with a substance 472,such as a gel or saline, which transmits the ultrasonic energy to thetissue. The device 462 may be operated in any mode or method describedherein.

[0214] Referring to FIGS. 69-70, another transducer 474 is shown whichmay be used with any of the devices described herein and is particularlyuseful with the devices of FIGS. 59-68 and all uses and features of thedevices described herein are incorporated here. The transducer 474preferably provides focused ultrasound relative to a focal axis FAwithin focal lengths and/or angle ranges described above. The transducer474 also provides diverging ultrasound energy when viewed along an axistransverse to the focal axis (FIG. 70). The ultrasound diverges to forman angle A2 of about 10 to 120 degrees and preferably about 45 degrees.The focused and diverging ultrasound is preferably formed with thesaddle-shaped transducer 474 with a similarly shaped layer 476 attachedor otherwise acoustically coupled thereto. Of course, the focused anddiverging ultrasound may be produced in any other suitable mannerincluding those described herein. An advantage of the diverging natureof the ultrasound energy is that tissue lying beneath gaps between cellscan be ablated with the ablating elements while still providing arelatively focused energy. The term focal axis FA, as defined herein, isintended to include both linear and non-linear shapes. For example, thefocal axis FA of the transducer of FIGS. 69 and 70 is curved.

[0215] Referring to FIGS. 71-73, still another ablating device 478 isshown wherein the same or similar reference numbers refer to the same orsimilar structure. The ablating device 478 has a first ablating element480, a second ablating element 482 and a third ablating element 484which differ. Although only three different ablating elements are shown,the device 478 could include any number of ablating elements. Theablating elements differ to provide different ablating characteristics.For example, the ablating elements may produce focused ultrasound withthe first ablating element having a different focal length than thesecond or third ablating elements. Such a configuration permits the userto select the appropriate ablating element for the particular tissuestructure. The ablating elements 480, 482 and 434 may also be designedto operate at different frequencies and/or powers.

[0216] The ablating elements are movable within a lumen 486 in a body488. The body 488 forms two suction channels 490 to adhere the device tothe target tissue. The body 488 preferably forms a closed loop but maybe shaped in any other manner. Each of the ablating elements has anelement 492 which transmits the ultrasound energy to the target tissue.The ablating elements may also have the membrane (see FIG. 64) or may beused without the element or membrane (see FIG. 60). Lumens 491 forsupply of energy, suction and inlet and outlet for the cooling mediumare provided. The lumens 491 extend through a manipulator 493. Themanipulator 493 forms a seal with the body 488 to adhere the body 488 tothe tissue with a suction.

[0217] An advantage of using ultrasound for ablation is that thetransducer may also be used to measure temperature. Measuringtemperature is particularly helpful in operating the transducer forfeedback control of the ablating element in any manner described above.Of course, the thermocouples described above or any other suitablemethods or devices for measuring temperature may be used.

[0218] Another advantage of using the transducer is that the transducercan be used to determine whether the transducer itself is in goodcontact with the tissue to be ablated. Any air gap between thetransducer and the near surface NS can dramatically affect the abilityto deliver the ultrasonic energy in a controlled manner. The adequacy ofcontact is determined by measuring the electrical impedance which isgenerally large when an air gap exists between the transducer andtissue. Monitoring suction as described above is another method ofassessing contact between the device and tissue.

[0219] Yet another advantage of using the transducer is that thetransducer can provide flow velocity data using conventional dopplertechniques. The doppler flow techniques can be used to characterize theamount of cooling at the far surface FS which can be used to select theappropriate tissue ablation technique.

[0220] Still another advantage of the transducer is that the transducercan provide the thickness of one or more layers of tissue using knownpulse-echo or a-line techniques. For example, the transducer may beoperated to provide total tissue thickness or the thickness of fat andmuscle or other layers. The thickness of fat, muscle, and totalthickness may be used when characterizing the tissue to determine theappropriate ablation technique. For example, the ablating element may beoperated in response to the tissue thickness measurement with or withoutone or more additional measurements. A single transducer may be used toemit ultrasonic energy and receive reflected energy or one transducermay emit and a different transducer can receive the reflected ultrasoundenergy.

[0221] The transducer may also be used to determine the distance totissue beyond the target tissue such as endocardial tissue on theopposite side of a cardiac chamber. Such measurements can be useful inselecting the appropriate transducer. For example, if the tissuestructure beyond the target tissue is relatively far away, a longerfocal length can be used since the ultrasound energy will be spread overa larger area. On the other hand, if the tissue structure is near thetarget tissue, shorter focal lengths may be preferred to avoid damagingthe tissue structure beyond the target tissue.

[0222] These above-described aspects of the ablating element may becombined with any of the other features and advantages of the invention.For example, the transducer 406 may be used for temperature feedbackcontrol of the control system 334 in any manner described herein and theflow velocity measurements may be used to characterize the amount ofblood cooling at the far surface FS.

[0223] A method of ablating tissue is now described. The method isdescribed in connection with the ablating device 400 described above,however, the method may be practiced with any other suitable structureor device. The ablating device 400 is positioned against tissue to beablated and suction is initiated to hold the cells 402 to the tissue tobe ablated. The ablating device 400 may use any of the methods anddevices described above, such as temperature feedback control or methodsof checking the adequacy of contact, which are incorporated here. Aswill be explained below, the transducer 406 itself may be used todetermine the adequacy of the contact between the device and the tissue.In particular, the transducer 406 may also be used to determine whetherany air gaps exist between the transducer 406 and the tissue. After ithas been determined that the cells 402 are adequately adhered to thetissue, one or more of the cells 402 are activated to begin ablatingtissue.

[0224] In another aspect of the invention, the device is operated duringtwo different time periods while varying at least one characteristic ofthe device such as the frequency, power, position of the focus relativeto the tissue and/or ablating time. For example, the ablating device 400may be operated at varying frequencies over time to ablate tissue in acontrolled manner. Specifically, the ablating device is preferablyoperated to create a transmural lesion by controlling the delivery ofenergy to the tissue. Although it is preferred to vary the frequencywhen ablating the tissue, the device may, of course, be operated at asingle frequency without departing from various other aspects of theinvention

[0225] In a first treatment method of the present invention, thetransducer 406 is activated at a frequency of 2-7 MHz, preferably about3.5 MHz, and a power of 80-140 watts, preferably about 110 watts, inshort bursts. For example, the transducer 406 may be activated for0.01-1.0 second and preferably about 0.4 second. The transducer 406 isinactive for about 2-90 seconds, more preferably 5-80 seconds, and mostpreferably about 45 seconds between activations. In this manner, acontrolled amount of accumulated energy can be delivered to the tissuein short bursts to heat tissue at and near the focus and minimizes theimpact of blood cooling at the far surface FS. Ablation at thisfrequency may continue until a controlled amount of energy is deliveredsuch as about 0.5-3 kilojoules. Treatment at this frequency inrelatively short bursts produces localized heating at the focus. At thefirst frequency, energy is not absorbed as quickly in tissue as it is athigher frequencies so that heating at the focus is not significantlyaffected by absorption of ultrasound energy in tissue before reachingthe focus.

[0226] Following treatment at the first frequency, the transducer 406 isoperated for longer periods of time, preferably about 1-4 seconds andmore preferably about 2 seconds, to ablate tissue between the focus andthe transducer 406. The frequency during this treatment is also 2-14MHz, more preferably 3-7 MHz and preferably about 6 MHz. The transducer406 is operated for 0.7-4 seconds at a power of 20-60 watts, preferablyabout 40 watts. The transducer 406 is inactive for at least 3 seconds,more preferably at least 5 seconds and most preferably about 10 secondsbetween each activation. In this manner, a controlled amount of energycan be delivered to heat tissue between the focus and the transducer.The treatment at this frequency may continue until a controlled amountof total energy is delivered such as about 750 joules.

[0227] As a final treatment, the ultrasonic transducer is activated at ahigher frequency to heat and ablate the near surface NS. The transduceris preferably operated at a frequency of at least 6 MHz and morepreferably at least 10 MHz and most preferably about 16 MHz. Thetransducer 406 is operated at lower power than the treatment methodsabove since the ultrasonic energy is rapidly absorbed by the tissue atthese frequencies so that the near surface NS is heated quickly. In apreferred method, the transducer is operated at 2-10 watts and morepreferably about 5 watts. The transducer 406 is preferably operateduntil the near surface NS temperature reaches 70-85 degrees C.

[0228] Each of the treatments described above may be used by itself orin combination with other treatments. Furthermore, the combination oftransducer size, power, frequency, activation time, and focal length mayall be varied to produce the desired delivery of ultrasound energy tothe tissue. As such, it is understood that the preferred embodiment maybe adjusted by simply adjusting one or more of the characteristics and,thus, these parameters may be changed without departing from variousaspects of the invention. The treatment sequence described abovegenerally deliver energy closer to the near surface NS during the secondtreatment and even closer to the near surface NS for the thirdtreatment.

[0229] The focus of the ultrasound energy may also be moved relative tothe tissue to deliver energy to different depths in the tissue. Whenusing the devices of FIGS. 66 and 67, for example, the device can bemoved closer to and farther away from the target tissue with themembrane 460 conforming to the required shape to fill the gap betweenthe transducer 406 and the tissue. The membrane is preferably inflatedand deflated to move the focus, however, the device may also be movedwith any other suitable mechanism such as the threaded foot describedabove. The focus may be moved while the ablating element is activated ormay be moved between activations of the ablating element. Moving thefocus of the ultrasound energy may be sufficient to create a transmurallesion without changing frequencies or may be used together with achange in frequencies as described above. The focus may be moved in anyother manner such as with a phased array or variable acoustic lensing.

[0230] Referring again to FIG. 60, after the ablating elements have beenactivated to ablate tissue it may be necessary to ablate tissue in gapsbetween ablations from each of the cells. In one method, the entiredevice is shifted so that each of the ablating elements is positioned toablate tissue beneath one of the gaps. Thus, after ablating tissue withall of the cells, the device is shifted and all of the cells areactivated again to create a continuous lesion. Another method to ablatetissue beneath the gaps is to tilt the cells to ablate tissue beneaththe gaps. In this manner, the device does not need to be moved. Whenusing the device of FIGS. 67, for example, the membrane is inflated totilt the transducer which directs the ultrasound energy toward tissuebeneath gaps between transducers.

[0231] The control system 334 may be designed to automatically ablate inany manner described herein. For example, the control system can changethe frequency, power, focal length and/or operating time to provide thedesired ablating technique. The change in frequency and power may becompletely automatic or may require some user input such as visualindications of fat and/or tissue thickness. For example, the controlsystem 334 may be designed to automatically sequence through two or moredifferent ablating techniques such as those described above. Othertechniques, of course, may be used depending on the tissuecharacteristics and the type and characteristics of the one or moreultrasound transducers 406. The control system 334 may also utilizefeedback, such as temperature-based feedback or electrical impedance, toactively control the ablations. Furthermore, although various methodshave been described, the corresponding functionality of the controlsystem is provided. Thus, all methods of the present invention providecorresponding devices and systems as controlled by the control system.

[0232] In still another aspect of the present invention, a cover 500 isprovided in which an ablating device 502 is positioned during initialpositioning of the device as shown in FIG. 74. The cover 500 may extendover only the bottom or contact surface of the ablating device 502 ormay be a sleeve 501 which surrounds the device 502. The ablating device502 may be any of the ablating devices, elements or systems describedherein or any other suitable system and all aspects of the ablatingdevices described herein are incorporated here specifically for theablating device 502. The cover 500 has a cavity 503 which contains aflowable material 504. The flowable material 504 provides an interfacebetween the ablating device 502 and the tissue to be ablated. Theablating device 502 is loaded into the cover 500 to help reduce oreliminate air bubbles or gaps contained in the flowable material 504.Air bubbles or air gaps can reduce the performance of various energysources such as RF and ultrasound.

[0233] The cover 500 is positioned at or near the desired ablatinglocation and the cover 500 is then pulled, retracted or otherwise movedto expose the ablating device 502. When the cover 500 is moved to exposethe ablating device 502, the flowable material 504 conforms to the shapeof the target tissue to provide an interface of the flowable material504 between the ablating device 502 and the target tissue. The cover 500is moved by simply pulling the sleeve over the end of the ablatingdevice 502 while maintaining the ablating device in substantially thedesired ablating position. Alternatively, the ablating device 502 may bemoved out of the cover 500, however, removal of the cover 500 ispreferred to prevent loss of the flowable material 504 as the ablatingdevice 502 is moved along the target tissue. The flowable material 504may be any suitable material depending upon the ablating energy beingused. When ultrasound energy is used, the flowable material ispreferably PEG (polyethyleneglycol) or glycerine. The flowable materialalso preferably has a relatively high boiling point such as at least 100degrees C. and a vapor pressure lower than that of water.

[0234] In still another aspect of the present invention, the ablatingdevice 502 may also have a tip 510 which provides a flexible, atraumaticdistal end as shown in FIG. 74. The flexible tip 510 facilitatesadvancement of the device 502 through the space between the epicardiumand pericardium without damaging the heart or pericardium. The tip 510may be removable so that the tip 510 does not interfere with theablating process and can make it easier to form a closed loop as isshown in various embodiments contained herein. It can be appreciatedthat the tip 510 may be used with any of the ablating devices, systemsor methods described herein without departing from this aspect of theinvention. The tip 510 preferably has a length of at least two inchesand more preferably at least four inches from the distal end 511. Thetip 510 is preferably free of any ablating elements.

[0235] In another aspect of the present invention, another system andmethod for ablating tissue is shown in FIGS. 75 and 76. The system 512provides a liquid environment around the heart. The liquid environmentmay help in energy transfer when using certain energy types, such as RFor ultrasound, and/or may serve to simply eliminate air bubbles or gapswhich can hinder energy transfer. The liquid environment also helps incontrolling the temperature since the temperature of the liquid can beregulated. For example, the liquid can be circulated through a heatexchanger 514 which heats or cools the liquid as desired. In one aspectof the invention, the liquid is cooled to remove heat generated by theablating device 502. The temperature may be controlled in any mannerdescribed herein and such methods are specifically incorporated here.

[0236] The system 512 includes a liquid delivery element 516, such as atube 518, connected to a liquid source 520, preferably sterile saline.Of course, the liquid must also be delivered and/or withdrawn with theablating device 502. Liquid is delivered as necessary with conventionalvalves 522 and clamps 524 controlling the flow of liquid. The ablatingdevice 502 is submerged within the liquid environment and may be anydevice described herein or other suitable device. The liquid deliveryelement 516 may form a fluid tight seal with the pericardium or thepatient may be positioned so that the liquid environment can be createdby penetrating the pericardium at an elevated position which does notrequire a hemostatic seal. The system 512 may be used in an open chestprocedure with a rib retractor 515 as shown in FIG. 76. The pericardiumis snared, sutured or otherwise anchored or suspended as is known in theart. The system 512 may also be used in a less or minimally invasivemanner as shown in FIG. 75 wherein the chest is accessed via asubxyphoid approach. The delivery element 516 has two lumens with one ofthe lumens 517 being an outlet lumen coupled to openings 519.

[0237] In another aspect of the invention, any of the ablating devicesdescribed herein may have a convex contact surface 520 as shown in FIGS.73 and 74. The convex contact surface 520 helps to squeeze or eliminateair bubbles or gaps from the area between the device and the targettissue. Air bubbles or gaps can inhibit energy transfer and, inparticular, can reduce the efficiency of ultrasound and RF energytransfer. The convex surface 520 may form part of the ablating elementitself or may be a separate element that is adhered, mounted orotherwise coupled to the ablating device as described above. Of course,the convex contact surface 520 may be used with any of the ablatingdevices described herein and is shown specifically in FIGS. 73 and 74.The convex contact surface 520 may be made of any suitable material suchas polyurethane.

[0238] Referring to FIGS. 77 and 78, another ablating device 522 isshown which is similar to the device of FIG. 64 wherein all aspects ofthe device of FIG. 64 are incorporated here. The ablating device 522 hasthe membrane 460 which is spaced apart from the ablating element to forma fluid cavity 524 therebetween. The fluid cavity 524 contains a fluid526 which can serve any one or more of the following functions. Thefluid 526, of course, transmits energy from the ablating element. Themembrane 460 also conforms to the shape of the target tissue. The fluid526 may be delivered from the source of cooling medium 434 having asuitable heat exchanger as discussed above. The temperature of the fluid526 may be controlled in any manner described herein and all suchdescriptions are incorporated specifically here for all purposes. Forexample, temperature control of the fluid provides the ability tocontrol the near surface temperature of the tissue in any mannerdescribed herein.

[0239] Referring to FIG. 77, each fluid cavity 524 may extend over asingle ablating element with each of the fluid cavities 524 beingcoupled to a common inlet lumen 530 and outlet lumen 531. Alternatively,the membrane 460 may extend over a number of ablating elements or alongthe entire device as shown in FIG. 78. The fluid 526 is circulatedthrough the fluid cavity 524 from an inlet lumen 525 attached to one endand an outlet lumen 527 attached to the other end of the device. Thefluid 526 is circulated through the fluid cavity 524 using the source ofcooling medium 434. The membrane 460 may also have openings 462 (FIG.77) therein or may be permeable so that some of the fluid 526 leaksthrough the membrane 460. The fluid 526 may help conduct energy or maysimply reduce or eliminate air gaps. The membrane 460 may also form theconvex contact surface 520 naturally or when fluid pressure is applied.The fluid 526 may also be pulsed to provide intermittent weeping orleaking of the fluid through the membrane 460. The pulsed fluid flow mayalso be used to deform the membrane by partially inflating/deflating themembrane which may help to sweep away bubbles or provide a flushingaction for the fluid.

[0240] Referring now to FIG. 79, a flexible skirt 536 may be providedaround the ablating element. The flexible skirt 536 may be used tocontain the fluid 526 which is supplied in any suitable manner such asthose described herein. Referring to FIG. 80, the flexible skirt may beused in connection with the convex contact surface 520. The fluid 526,or other flowable material, is introduced through an inlet 540 andtravels down lumen 542 to the contact surface 520. The skirt 536 helpsto contain the fluid 526 to inhibit the fluid 526 from flowing freelyoutward.

[0241] Finally, although the present methods have been described inconnection with creating a continuous lesion around the pulmonary veins,it is understood that the methods are equally applicable for onlyablating partially around the pulmonary veins or along only a segment.Furthermore, other lesions may be beneficial in treatingelectrophysiological conditions and the devices and methods describedherein may be useful in creating such other lesions. Thus, the presentinvention should not be construed as being limited to creating lesionscompletely around the pulmonary veins.

[0242] While the above is a complete description of the preferredembodiments of the invention, various alternatives, substitutions andmodifications may be made without departing from the scope thereof,which is defined by the following claims. For example, any of theablating devices described herein may have the anchor, fins, lateralballoons, sensors, and/or electrodes without departing from the scope ofthe invention.

What is claimed is:
 1. A device for ablating tissue, comprising: anablating device having at least one ablating element and a bottomsurface, the bottom surface being positioned adjacent to tissue to beablated; and a cover extending over the bottom surface; a cavity definedby a space between the cover and bottom surface; and a flowable materialpositioned in the cavity; wherein the cover is movable relative to theablating device to a position which exposes the bottom surface whileleaving the flowable material positioned between the ablating device andthe tissue to be ablated.
 2. The device of claim 1, wherein: theablating device has a removable tip.
 3. The device of claim 1, wherein:the flowable material has a boiling temperature of at least 100 degreesC. and a vapor pressure higher than water.
 4. The device of claim 1,wherein: the flowable material is selected from the group consisting ofPEG and glycerine.
 5. The device of claim 1, wherein: the ablatingdevice has a plurality of ablating elements.
 6. The device of claim 1,wherein: the ablating device forms a closed loop.
 7. The device of claim1, wherein: the cover is a sleeve which surrounds the ablating device.8. A method of ablating tissue, comprising the steps of: providing anablating device and a cover, the ablating device having a bottomsurface, the cover being spaced apart from the bottom surface to definea fluid cavity, the fluid cavity containing a fluid; positioning thecover against a tissue surface; moving the cover away from the bottomsurface so that the bottom surface is exposed and positioned adjacentthe tissue surface, the flowable material conforming to the shape of thetissue surface and being positioned between the bottom surface of theablating device and the tissue surface; and ablating the tissue afterthe moving step.
 9. The method of claim 8, wherein: the positioning stepis carried out with the tissue surface being an epicardial surface. 10.The method of claim 8, wherein: the moving step is carried out by movingthe cover while substantially maintaining the position of the ablatingdevice.
 11. The method of claim 8, wherein: the providing step iscarried out with the cover having a removable tip.
 12. The method ofclaim 8, wherein: the providing step is carried out with the flowablematerial having a boiling temperature of at least 120 degrees C.
 13. Themethod of claim 8, wherein: the providing step is carried out with theflowable material being selected from the group consisting of PEG andglycerine.
 14. The method of claim 8, wherein: the providing step iscarried out with the ablating device having a plurality of ablatingelements.
 15. The method of claim 8, wherein: the providing and movingsteps are carried out with the ablating device forming a closed loop.16. The method of claim 15, wherein: the providing and moving steps arecarried out with the ablating device forming a closed loop around thepulmonary veins; and the ablating step is carried out to form anablation around the pulmonary veins.
 17. A device for ablating tissue,comprising: a body having a first part and a second part which arecoupled together to form a closed loop and separated to open the closedloop; at least one ablating element mounted to the body; and a flexibletip extending from an end of the body, the tip extending for at leasttwo inches and being free of any ablating elements, the flexible tipfacilitating advancement of the body through a space between theepicardium and pericardium.
 18. The device of claim 17, wherein: the tipis removable from the body.
 19. The device of claim 17, wherein: thebody has a plurality of ablating elements attached thereto.
 20. Thedevice of claim 17, wherein: the ablating device has an ultrasonictransducer.
 21. The device of claim 17, wherein: the body has a convexbottom surface which is positioned adjacent the tissue to be ablated.22. The device of claim 21, wherein: a membrane forms the convexsurface.
 23. The device of claim 22, wherein: the membrane partiallydefines a cavity containing a fluid.
 24. The device of claim 17,wherein: the ablating device has a plurality of ablating elements. 25.The device of claim 17, wherein: the ablating device forms a closed looparound the heart.
 26. A system of forming an ablation from an epicardiallocation, comprising the steps of: a liquid delivery device fordelivering a liquid to a space between the pericardium and epicardium tocreate a liquid environment around the heart; and at least one ablatingelement for ablating tissue when submerged in the liquid environmentaround the heart.
 27. The system of claim 26, wherein: the ablatingelement is an element selected from the group consisting of RF,ultrasound, microwave, cryo and laser
 28. The system of claim 26,wherein: the liquid delivery device is delivered through a penetrationin the pericardium.
 29. A method of ablating tissue from an epicardiallocation, comprising the steps of: providing an ablating device having atip; advancing the ablating device through a space between theepicardium and pericardium; removing the tip of the ablating device; andablating tissue with the ablating device.
 30. The method of claim 29,further comprising the step of: forming a closed loop with the ablatingdevice after the removing step.
 31. The method of claim 29, wherein: theadvancing step is carried out with the ablating device having aplurality of ablating elements.
 32. The method of claim 29, wherein:ablating step is carried out to form an ablation around the pulmonaryveins.
 33. The method of claim 29, wherein: the providing step iscarried out with the tip having a length of at least two inches andbeing free of ablating elements.
 34. The method of claim 33, wherein:the providing step is carried out with the tip having a length of atleast four inches.
 35. A method of forming an ablation from anepicardial location, comprising the steps of: creating a liquidenvironment around a patient's heart; positioning an ablating deviceagainst an epicardial location of the patient's heart; and ablatingtissue from the epicardial location while the ablating device iscontained within the liquid environment.
 36. The method of claim 35,wherein: the creating step is carried out by at least partially fillingthe pericardial space with the liquid to create the liquid environmentaround the patient's heart.
 37. The method of claim 35, wherein: theablating step is carried out with the ablating device being submergedwithin the liquid.
 38. The method of claim 35, wherein: the creatingstep is carried out with the liquid environment being contained by thepericardium.
 39. The method of claim 35, wherein: the ablating step iscarried out with the ablating device having an ablating element whichuses RF, ultrasound, laser, cold or microwave.
 40. The method of claim35, wherein: the creating step is carried out with the pericardium beingincised to create an opening, the fluid environment having an exposedfree surface of the liquid.
 41. The method of claim 35, wherein: thecreating step is carried out with the ablating device passing through apenetration in the pericardium.
 42. A method of ablating tissue,comprising the steps of: providing an ablating device having a convexcontact surface; positioning the convex contact surface adjacent to anepicardial surface; ablating the epicardial tissue after the positioningstep.
 43. The method of claim 42, wherein: the providing step is carriedout with the ablating device comprising an ultrasonic transducer. 44.The method of claim 43, wherein: the providing step is carried out withthe convex surface being formed by an element mounted to the ultrasonictransducer.
 45. The method of claim 44, wherein: the providing step iscarried out with a membrane forming the convex surface.
 46. The methodof claim 45, wherein: the providing step is carried out with themembrane partially defining a cavity containing a fluid.
 47. The methodof claim 42, wherein: the providing step is carried out with theablating device having a plurality of ablating elements.
 48. The methodof claim 42, wherein: the providing and moving steps are carried outwith the ablating device forming a closed loop around the heart.
 49. Themethod of claim 48, wherein: the providing and moving steps are carriedout with the ablating device forming a closed loop around the pulmonaryveins; and the ablating step is carried out to form an ablation aroundthe pulmonary veins.
 50. An ablating device for ablating tissue,comprising: a body; an ablating element coupled to the body; a membraneextending over at least part of the ablating element, the membrane beingspaced apart from the ablating element to form a fluid cavity; and thefluid cavity containing a fluid.
 51. The ablating device of claim 50,further comprising: a fluid source coupled to the fluid inlet forcirculating the fluid through the fluid cavity.
 52. The ablating deviceof claim 51, further comprising: a heat exchanger having an inlet whichreceives the fluid and an outlet which returns the fluid to the fluidcavity.
 53. The ablating device of claim 50, wherein: the membrane formsa convex contact surface.
 54. The ablating device of claim 50, wherein:the membrane forms the convex contact surface with fluid pressure. 55.The ablating device of claim 50, wherein: the membrane permits some ofthe fluid to pass therethrough to wet the target tissue with the fluid.56. The ablating device of claim 50, wherein: the membrane extends overmore than one ablating element.
 57. An ablating device for ablatingtissue, comprising: a body; an ablating element coupled to the body; aflexible skirt surrounding at least a portion of the ablating element;the fluid cavity containing a fluid.
 58. The ablating device of claim57, further comprising: a fluid delivery channel which delivers fluid tothe fluid cavity.
 59. The ablating device of claim 57, wherein: the bodyhas a contact surface on a bottom side, the contact surface beingconvex.
 60. A method of ablating tissue from an epicardial locationusing a device according to claims 51-59.